(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Voluntary intake as affected by age and size of sheep and quality of forage"

VOLUNTARY INTAKE AS AFFECTED BY AGE AND SIZE OF 
SHEEP AND QUALITY OF FORAGE 



By 

FAUSTO A. CAPOTE FERRER 



A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF 

THE UNIVERSITY OF FLORIDA 
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE 
DEGREE OF DOCTOR OF PHILOSOPHY 



UNIVERSITY OF FLORIDA 
1975 



To the memory of my father: 
DR. FAUSTO R. CAPOTE CALLEJAS 



ACKNOWLEDGEMENTS 

The author is sincerely grateful to his major profes- 
sor, Dr. John E. Moore, for his professional guidance and 
assistance throughout the experimental investigation and 
valuable suggestions in the writing of this, dissertation; 
and also to Drs. C. B. Ammerman, L. R. McDowell, G. 0. Mott 
and C. J. Wilcox for valuable advice as members of the Super- 
visory Committee. 

The statistical guidance of Drs. C. J. Wilcox and 
R. C. Littell is deeply appreciated. He wishes to thank 
Drs. J. W. Carpenter, A. Z. Palmer and R. L. West for their 
advice and generous cooperation with the slaughtering and 
the evaluation of carcasses. 

He is grateful for the assistance and friendship 
given him by many of the graduate students, especially J. T. 
Perdomo, E. J. Golding, III, W. A. Brommelsiek, C. A. Turner, 
L. C. Martin, S. L. Hansard and L. E. Eubanks. Thanks are 
also due to J. D. Funk and P. Cowvins for the aid in the 
field work. 

The author is indebted to his wife, Amelita, for her 
understanding, and patience during the period of academic 
hardship, her helpful assistance and comments in the prepa- 
ration of the manuscript. To his mother, and to his children, 



111 






a very special thanks for their love and encouragement. 

Acknowledgement is made to the Facultad de Ciencias 
Veterinarias de la Universidad del Zulia for giving him the 
opportunity to carry out a graduate program at the University 
of Florida. 

The author wishes to thank Mrs. H. Fung for typing 
this dissertation. 



i v 



TABLE OF CONTENTS 

Page 

ACKNOWLEDGMENTS iii 

LIST OF TABLES viii 

LIST OF APPENDIX TABLES x 

LIST OF FIGURES xii 

ABSTRACT xiii 

INTRODUCTION . • 1 

REVIEW OF LITERATURE . 3 

Control of Voluntary Intake in Ruminants 3 

The Neural Basis of Intake Control 3 

Theories on Regulation of Feed Intake 5 

Glucostatic regulation 6 

Thermostatic regulation ... 7 

Lipostatic regulation 9 

Hormones 12 

Humoral factor 14 

Amino acids and minerals 15 

Rumen metabolites 16 

Ruminal distention 18 

Integration of Physical and Chemostatic Theories 23 

Effects of Animal Characteristics on Voluntary 
Intake 25 

Body Size and Age 25 

Age, Size and Diet Interaction 28 

Rate of Pro duct ion 32 

Fatness 33 

Exponents Relating Body Weight to Nutrient Intake . 35 



TABLE OF CONTENTS - Continued 

Page 

EXPERIMENT I. REPEATABILITY OF VARIOUS EXPRESSIONS 

OF FORAGE INTAKE 43 

Procedure 43 

Experimental Design 43 

Intake and Digestion Trial Procedure 45 

Laboratory Analysis 46 

Between-Trial Management of Animals 47 

Statistical Analysis 47 

Results and Discussion 48 

Forage Composition 48 

Live Weight Changes 48 

Nutrient Digestibility 51 

Voluntary Intake 51 

Relationship between intake and age 51 

Relationship between intake and live weight . 61 

Repeatability of Voluntary Intake 63 

Regression Analysis of Forage Intake on Body 

Weight 68 

Removal of Body Size Effect on Intake 71 

EXPERIMENT II. EFFECT OF ANIMAL AGE, SIZE, AND FATNESS 

ON VOLUNTARY INTAKE OF PELLETED FORAGES 76 

Procedure , 76 

Experimental Design 76 

Live Animal Weighing 78 

Carcass Measurements ". 78 

Statistical Analysis 79 

Results and Discussion 79 

Forage Composition 79 

Animal Age and Digestibility 80 

Animal Age, Body Size and Voluntary Intake ... 80 
Statistical Variation Associated with Different 

Expressions of Intake Relative to Body Size . . 84 
Interrelationships Among Animal Age, Body Weight, 

Degree of Fatness and Voluntary Intake 89 



vi 



TABLE OF CONTENTS - Continued 

Page 
GENERAL DISCUSSION 94 

Digestibility 94 

Voluntary Intake 98 

Repeatability of Voluntary Intake 103 

Intake and Body Size 107 

Intake, Age and Animal Condition 109 

SUMMARY AND CONCLUSIONS . . ." m 

APPENDIX 114 

LITERATURE CITED 139 

BIOGRAPHICAL SKETCH 161 



vii 



LIST OF TABLES 



Table Pa 9 e 

1 REFERENCE BASE OF BODY WEIGHT FROM THE RELA- 
TION OF INTAKE TO ANIMAL BODY WEIGHT AS RE- 
PORTED BY VARIOUS SOURCES IN THE LITERATURE . . 39 

2 ARRANGEMENT OF TREATMENTS. EXPERIMENT I . . . . 44 

3 CHEMICAL COMPOSITION AND J_N VITRO DIGESTION 

OF THE FORAGES. EXPERIMENT I 49 

4 INTAKE OF DIGESTIBLE NEUTRAL DETERGENT 
FIBER (NDF) AT DIFFERENT AGES OF THE 

ANIMAL. EXPERIMENT I 59 

5 EXCRETION OF UNDIGESTED NEUTRAL DETERGENT 
FIBER AND NEUTRAL DETERGENT SOLUBLES AT 
DIFFERENT AGES OF THE ANIMAL. EXPERIMENT I. . . 60 

6 VOLUNTARY INTAKE OF ORGANIC MATTER AND 
NEUTRAL DETERGENT FIBER EXPRESSED AS FUNC- 
TIONS OF BODY WEIGHT AND METABOLIC SIZE 

ACROSS AGES. EXPERIMENT I 62 

7 VARIABILITY ASSOCIATED WITH DIGESTIBLE ORGAN- 
IC MATTER INTAKE EXPRESSED IN TERMS OF ABSO- 
LUTE VALUES AND AS FUNCTION OF BODY WEIGHT 

(wj.* ) AND METABOLIC SIZE (W^ 5 )- EXPERIMENT I. 64 

8 ESTIMATES OF REPEATABILITY (R) OF INTAKE 
EXPRESSIONS. AND STANDARD ERROR (SE) OF 
REPEATABILITY. EXPERIMENT I 66 

9 REGRESSION COEFFICIENTS AND STATISTICS OF FIT 
FOR THE LOGARITHMIC REGRESSION OF DIGESTIBLE 
ORGANIC MATTER INTAKE (Y) ON BODY WEIGHT (X). 
EXPERIMENT I 69 



VI 1 1 



LIST OF TABLES - Continued 



Table Page 

10 REGRESSION COEFFICIENTS AND STATISTICS 
OF FIT FOR THE LINEAR REGRESSION OF TWO 
EXPRESSIONS OF DIGESTIBLE ORGANIC MAT- 
TER INTAKE. EXPERIMENT I 73 

11 FACTORIAL ARRANGEMENT OF TREATMENTS. 

EXPERIMENT II 77 

12 CHEMICAL COMPOSITION AND IN VITRO DIGESTION 

OF THE FORAGES FED IN EXPERIMENT II 81 

13 EFFECT OF AGE AND FORAGE QUALITY ON NUTRI- 
ENT DIGESTIBILITY. EXPERIMENT II 82 

14 SIMPLE STATISTICS OF DIFFERENT FORMS OF 
EXPRESSION OF BODY SIZE. EXPERIMENT II . . . 86 

15 SIMPLE STATISTICS ASSOCIATED WITH EXPRES- 
SIONS OF VOLUNTARY INTAKE RELATIVE TO BODY 

SIZE. EXPERIMENT II 88 

16 LINEAR REGRESSION EQUATIONS AND STATISTICS 
OF FIT FOR RELATIONSHIPS AMONG VARIOUS BODY 
MEASUREMENTS. EXPERIMENT II 90 

17 REGRESSION COEFFICIENTS AND STATISTICS OF 
FIT FOR THE MULTIPLE LOGARITHMIC REGRESSION 
OF DIGESTIBLE ORGANIC MATTER INTAKE (Y) ON 
FULL BODY WEIGHT, CARCASS FAT AND ANIMAL 

AGE. EXPERIMENT II 93 

18 SUMMARY OF STEPWISE REGRESSION OF DIFFERENT 
VARIABLES ON UNDIGESTIBLE NEUTRAL DETERGENT 
SOLUBLES 99 

19 'BEST' FOUR VARIABLE MODELS FOR UNDIGESTIBLE 
NEUTRAL DETERGENT SOLUBLES PREDICTION FOUND 

BY THE MAXIMUM R-SQUARE IMPROVEMENT PROCEDURE 100 

20 MOST PROBABLE VOLUNTARY NEUTRAL DETERGENT 
FIBER INTAKE OF A HYPOTHETICAL SHEEP, AND . 
GAIN IN ACCURACY OF PREDICTION BY REPEATED 
MEASUREMENTS 106 



IX 






LIST OF APPENDIX TABLES 



Table 



Page 



21 DIGESTIBILITY AND VOLUNTARY INTAKE OF NUTRI- 
ENTS AT DIFFERENT AGES OF THE ANIMAL. EXPERI- 
MENT I 

22 VOLUNTARY INTAKE OF DIGESTIBLE ORGANIC MATTER 
AND NEUTRAL DETERGENT FIBER EXPRESSED AS FUNC- 
TIONS OF BODY WEIGHT AND METABOLIC SIZE ACROSS 
AGES. EXPERIMENT I 

23 CORRELATION MATRIX OF SELECTED FORAGE EVALUA- 
TION PARAMETERS. EXPERIMENT I 

24 LOGARITHMIC REGRESSIONS OF INTAKE VARIABLES 
(Y) ON BODY WEIGHT (X). EXPERIMENT I .... 

25 POOLED WITHIN AGES LOGARITHMIC REGRESSIONS 
OF INTAKE VARIABLES (Y) ON BODY WEIGHT (X). 
EXPERIMENT I 

26 REGRESSION COEFFICIENTS AND STATISTICS OF 
FIT FOR THE COMMON LOGARITHMIC REGRESSION OF 
INTAKE VARIABLES (Y) ON BODY WEIGHT (X). 
EXPERIMENT I 

27 REGRESSION COEFFICIENTS AND STATISTICS OF 
FIT FOR THE LINEAR REGRESSION OF INTAKE PER 

KILOGRAM BODY WEIGHT (wJo°) (Y) ON BODY 
WEIGHT (X). EXPERIMENT V 

°8 REGRESSION COEFFICIENTS AND STATISTICS OF 

FIT FOR THE LINEAR REGRESSION OF INTAKE PER 

KILOGRAM OF METABOLIC SIZE (W' 75 ) (Y) ON 
BODY WEIGHT (X). EXPERIMENT I Kg 

29 AGE AND FORAGE OUALITY EFFECT ON VOLUNTARY 
INTAKE EXPRESSED AS FUNCTION OF BODY WEIGHT. 
EXPERIMENT II 

30 CORRELATION MATRIX OF SELECTED CARCASS PARA- 
METERS. EXPERIMENT II 



115 



117 
118 
120 

121 



122 



123 



124 

125 

126 



LIST OF APPENDIX TABLES - Continued 



Table Page 

31 CARCASS CHARACTERISTICS OF THE EXPERIMENTAL 
ANIMALS. EXPERIMENT II 127 

32 LEAST SQUARES ANALYSIS OF VARIANCE FOR DI- 
GESTIBILITY AND INTAKE DATA. EXPERIMENT I . . 129 

33 LEAST SQUARES ANALYSIS OF VARIANCE FOR DI- 
GESTIBILITY AND INTAKE DATA. EXPERIMENT II. . 131 

34 LEAST SQUARES ANALYSIS OF VARIANCE OF 
SELECTED CARCASS CHARACTERISTICS. EXPERI- 
MENT II 133 

35 INDIVIDUAL DATA ON NUTRIENT DIGESTIBILITY 

AND VOLUNTARY INTAKE. EXPERIMENT I 134 

36 INDIVIDUAL DATA ON NUTRIENT DIGESTIBILITY 

AND VOLUNTARY INTAKE. EXPERIMENT II 137 



XT 






LIST OF FIGURES 

Figure Page 

1 Live weights recorded at initiation of 

each trial in Experiment I. 50 

2 Digestibility of organic matter in 

Experiment I 52 

3 Digestibility of neutral detergent fiber 

in Experiment I 53 

4 Voluntary intake of organic matter in 
Experiment 1 54 

5 Voluntary intake of neutral detergent 

fiber in Experiment I. 56 

6 Intake of digestible organic matter in 
Experiment I. 57 

7 Linear regression of digestible organic 
matter intake per kg of metabolic size 

on body weight. Experiment I 72 

8 Linear regression of digestible organic 
matter intake per kg of body weight on 

body weight. Experiment 1 74 

9 Intake of digestible organic matter at 

each forage-age combination. Experiment II.. . 83 

10 Intake of digestible organic matter per 
kg body weight at each forage-age combi- 
nation. Experiment II 85 

11 Effect of animal size and forage quality 

on carcass fat content. Experiment II 91 



xii 



Abstract of Dissertation Presented to the Graduate Council 
of the University of Florida in Partial Fulfillment of the 
Requirements for the Degree of Doctor of Philosophy 

VOLUNTARY INTAKE AS AFFECTED BY AGE-AND SIZE OF 
SHEEP AND QUALITY OF FORAGE 

By • 

Fausto A. Capote Ferrer 
December, 1975 

Chairman: Dr. John E. Moore 
Major Department: Animal Science 

Two experiments were conducted with the objective of: 
1) measuring the effect of age and body size of sheep on in- 
take and digestibility of three pelleted forages differing 
in nutritive composition, 2) estimating repeatability of 
voluntary intake and, 3) selecting an expression of volun- 
tary intake, related to body size, that would increase the 
usefulness of intake values as an index of forage quality. 

In experiment I a series of four intake and digesti- 
bility trials were conducted with a group of 24 Suffolk x 
Native crossbred wethers, randomly assigned to one of three 
pelleted forages: a) low quality Coastal bermudagrass 
( Cynodon dactylon ) (LQB) containing 7% crude protein (CP), 
b) high quality Coastal bermudagrass (HQB) containing 14% 
CP, and c) alfalfa ( M e d i c a g o s a t i v a ) (ALF) containing 17% 
CP. All diets were offered a_d 1 i bi turn , once daily, for a 
14-day preliminary period and a 7-day collection period. 
The animals averaged 10 months of age in trial I, and 28 



x i i i 






months in trial IV. In experiment II, a group of 36 Suffolk 
x Native wethers, representing three ages and different 
sizes within each age, were randomly assigned to two pelleted 
Coastal bermudagrass diets similar in composition and quality 
to the bermudagrass diets used in experiment I. Intake and 
digestibility of diets was measured as in experiment I. At 
the termination of the experiment these animals were slaugh- 
tered and some carcass measurements taken. 

Mean coefficients of OM digestibility for the LQB, 
HQB and ALF diets in experiment I were 41, 57 and 55%, re- 
spectively. Within a diet, digestibility coefficients 
showed yery small variability among animals and across ages 
(C.V. < 7%). Changes in digestibility coefficients were 
observed when determined at different ages of the animals. 
The trend approximated a curvilinear effect. Animal age 
per se, however, did not appear to exert a significant 
effect on digestibility. 

Intake of pelleted forage diets was more closely 
related to live weight (W " ) than to metabolic size (W ). 
Logarithmic regression of digestible organic matter (DOM) 
intake (g/day) on body weight (BW) indicated that the 
best reference base (exponent) of BW was 1.03 ± .09, 
.90 ± .09, and 1.07 ± .09, for the LQB, HQB, and ALFdiets, 
respectively. Neutral detergent fiber (NDF) concentration 
was the forage variable most highly correlated (r = -.77) 
with intake; and NDF intake was the expression of intake 



xiv 



best correlated (r = .89) with body size. Repeatability of 
intake ranged from .26 to .53, depending on the variable 
estimated. The highest repeatability (.53 ± .10) was ob- 



tained with NDF intake/W 



,1 .0 



kg 



The expression of intake that 



showed the minimum effect of body weight was DOM intake/W, 1 " 

kg 

Mean DOM intake values reflected the quality of the diet, 

and ranged from 12 to 23 grams/W? * °/day for the LQB and ALF 

Kg 

diets, respectively. 

In experiment II, multiple regression analysis of 
DOM intake on BW, carcass fat content and animal age demon- 
strated that body weight, rather than age, largely deter- 
mined animal potential for forage intake. Age showed a posi- 
tive, but non-significant, effect on DOM intake, whereas 
carcass fat exerted a negative effect, irrespective of diet 
quality. 



xv 



INTRODUCTION 

Forages have always been an essential feed ingredient 
in cattle feeding programs; however present and future out- 
looks make them the most important source of feed nutrients 
available for ruminant animals. 

In the in vivo evaluation of forages two major aspects 
are involved. One is the intrinsic nutritive value of the 
forage plant given by its chemical composition, energy digest- 
ibility, and biological value of digested products, which 
along with other animal related factors will influence its 
acceptability and consumption by the animal. The other 
aspect involved is that related to the experimental animal, 
its inherited genetic potential and nutrient demands. 

The forage aspect has been extensively studied and 
progress of such magnitude has been achieved that the nutri- 
tive value and digestibility of a given hay may be accurately 
predicted from routine laboratory analysis. The animal 
aspect has not received as much attention, but is gaining 
considerable importance as more research findings indicate 
the variability and problems associated with prediction of 
voluntary intake under given sets of nutritional conditions. 

Many factors affect the amount of food voluntarily 
consumed because, besides forage nutritive value and animal 



1 



genetic variation, factors such as age, body size, previous 
nutrition and condition of the animal, among others, will 
influence the amount of forage consumed. 

Crampton et al . (1960) fifteen years ago indicated 
that intake accounted for 70 percent of the variability of 
their Nutritive Value Index. Today, intake remains the 
most variable, least predictable, but most important of 
the forage quality components. 

From the standpoint of forage evaluation, therefore, 
we must characterize and weigh quantitatively each of the 
variables related to the forage and to the animal if we are 
to predict, with a practical degree of accuracy, the poten- 
tial value of a forage for animal production. 

The objectives of t h is dissertation were (1) to meas- 
ure the effect of age and body size of sheep on intake and 
digestibility of three pelleted forages differing in nutri- 
tive composition, (2) to estimate the repeatability of 
voluntary intake and, (3) to find an expression of intake, 
related to body size, that would increase the usefulness of 
intake values as an index of forage quality. 






REVIEW OF LITERATURE 



Control of Voluntary Intake in Ruminants 



The Neural Basis of Intake Control 



Most of the published work on mammalian food intake 
regulation has been conducted with non-ruminants. In the 
past years, however, there has been an increased interest 
in factors determining the food intake in ruminants. 

Much evidence supports the view that food intake 
regulation is ultimately mediated through the central 
nervous system (CNS). Anand (1961) postulated that there 
are various levels of nervous control over intake, from sim- 
ple spinal reflexes through the complex activities involving 
the cerebral cortex, which exercise control of a discrimi- 
native nature (Ulyatt, 1964). According to Lars son (1954), 
one region of the brain, the hypothalamus, has been impli- 
cated in the control of intake both in non-ruminants and 
ruminants . 

Two areas of the hypothalamus appear to be concerned 
in the regulation of food intake. The first is the region 
of the ventromedial nuclei (VMH), where electrolytic lesions 



resulted in a sustained hyperphagia and obesity in rats 
(Hetherington and Ranson, 1940, 1942). The same physiolog- 
ical response has been observed in other species of non- 
ruminants (Anand and Brobeck, 1951; Hamilton and Brobeck, 
1964). In ruminants, Baile et al . (1967a, b, c , 1963, 
1974) reported hyperphagia and rapid weight increases in 
goats with VMH lesions. Electrical stimulation of the VMH 
produces hypophagia or evidence of satiety (Andersson and 
Larsson, 1961; Anand, 1961), and that area has been called 
the "satiety center". 

The second area of the hypothalamus concerned with 
intake regulation is in the lateral hypothalamus (LH) where 
stimulation resulted in hyperphagia in rats ( Stei nbaum and 
Miller, 1965), goats (Baile et al . , 1967a, b; Larsson, 1954) 
and sheep (Larsson, 1954). Bilateral lesions of the LH 
caused temporary or permanent aphagia in rats (Teitelbaum 
and Epstein, 1952), goats (Baile et al . , 1968) and sheep 
(Tarttelin and Bell, 1968). The LH area has been called 
the "f eedi ng center" . 

Although there is evidence that voluntary intake is 
regulated by the CNS in non- rumi nants and ruminants, the 
details of the mechanisms, the sites of the receptors, and 
the nature of the stimuli which pass signals to the system 
in response to ingestion of food remain obscure and sub- 
ject to a great deal of investigation. There have been 
several theories proposed to attempt to explain observations 



and data. However, no single mechanism has been shown to 
give complete intake control, and the situation is even 
more complex when considering intake regulation in ruminants. 



Theories on Regulation of Food Intake 

Previous work on the regulation of ruminant intake 
has centered on two main theories: (a) Chemostati c, and 
(b) Physical. The first theory involves mechanisms that 
are chemical and physiological in nature, such as 1 i po- 
st a t i c , glucostatic and thermostatic mechanisms. Fatty 
acids, glucose, hormones, amino acids, and rumen volatile 
fatty acids, among others, have been suggested as metabo- 
lites acting as feedback signals in the regulation of 
energy balance. The physical theory, on the other hand, is 
based on ruminal distention, or gastrointestinal "fill", 
resulting from the ingestion of feed and influenced by the 
rate of disappearance of ingesta from the rumen. 

It has been shown that ruminants manage their energy 
balance under many conditions (Baile and Pfander, 1967; 
Campling, 1966; Dinius and Baumgardt, 1970; Hadjipieris 
and Holmes, 1966; Montgomery and Baumgardt, 1965a, b). En- 
ergy balance being determined by the difference between 
energy input (feed) and energy output (maintenance, produc- 
tion, reproduction, activity) (Baumgardt, 1970). Energy 
balance, therefore, may be considered as the regulated sys- 
tem and feed intake as an important regulator of the system 



(Baile, 1968). The system, called the controller system, 
involves various feedback signals that are generated by the 
consumption of a meal, the subsequent passage of residues 
through the gastrointestinal tract, and metabolism (Baumgardt, 
1970). 

According to Baile (1968), it is quite likely that 
at least two types of feedback systems exist: the first to 
help control meal size and frequency, and a second to help 
manage long-term energy balance. Short-term regulation of 
feed intake is concerned with the initiation and cessation 
of individual meals, and the feedbacks associated with 
short-term control may yery well differ from those for the 
control of long-term energy balance (Baumgardt, 1970). To 
be effective, the short-term feedback must change more ra- 
pidly than those for long-term control. Consequently, pos- 
sible factors acting as feedbacks may be useful to the ani- 
mal if they change in relation to feeding (Baile and Mayer, 
1970). The glucostatic and thermostatic regulatory mecha- 
nisms are most applicable to short-term control, whereas the 
lipostatic mechanism has been suggested as a possible long- 
term system. 

Glucostatic Regulation 

Mayer (1955) suggested with nonruminants that the 
short-term intake control mechanism might operate through 
hypothalamic gl ucoreceptors sensitive to blood glucose. In 



later work, Mayer (1963) indicated that arteriovenous glu- 
cose difference rather than concentration of blood glucose, 
was important in regulation of appetite. .Research with 
ruminants, however, indicates that blood glucose and insulin 
levels do not change appreciably with feeding (Manns and 
Boda, 1967). Intravenous (Dowden and Jacobson, I960), intra- 
peritoneal (Simkins et a! . , 1965) and/or i ntracerebral- 
ventricular (Baile and Mahoney, 1967) infusions of glucose 
have caused no appreciable effect on appetite. Baile and 
Mayer (1968c) and Baile and Martin (1971) reported that 
insulin-induced hypoglycemia failed to stimulate eating in 
ruminants. Thus, there is little evidence to indicate that 
the glucose state of the body plays a significant role in 
feed control in ruminants. 



Thermostatic regulation 

The possibility that food intake might be controlled 
by a thermoregulatory mechanism was postulated by Brobeck 
(1948, 1960). They suggested that "animals eat to keep 
warm and stop eating to prevent hyperthermia," and that the 
extra heat released during the assimilation of food (spe- 
cific dynamic action) provides the signal for short-term 
adjustments of food intake (Balch and Campling, 1962). Rumi- 
nants generally lose a greater proportion of their energy 
intake as specific dynamic action than non-ruminants 
(Blaxter, 1962). 



Andersson and Larsson (1961) demonstrated that cool- 
ing of an area in the hypothalamus induced eating shortly 
after a meal, but warming inhibited eating in a hungry goat. 
Bhattacharya and Warner (1968) reported that i ntra-rumi nal 
infusions of cold (5°C) water at 30 minutes intervals caused 
an increase in feed consumption by 24%, while infusion of 
warm (49°C) water depressed intake by 9%. Baile and Mayer 
(1968a) attempted to test for this feedback mechanism by 
measuring the hypothalamic, rum i nal, anterior vena cava, 
and horn temperatures of physically inactive goats. The 
animals were force-fed through rumen fistulae after a 16 
hour fast. Neither hypothalamic temperature increased nor 
was there evidence that the animals had activated their 
heat-loss mechanism since the horn temperature, a measure 
of vasodilation, did not increase. Dim" us et al . (1970) 
observed changes in hypothalamic temperatures with feeding 
but related these changes to activity rather than to food 
consumption per se . 

Ruminants do, however, adjust their feed intake in 
relation to a large change in environmental temperature. 
There have been many observations that ruminants eat less 
at high temperatures and more at low temperatures (Brobeck, 
1960). Martz et al . (1971) exposed steers fed a 60% con- 
centrate ration to varying environmental temperatures. When 
temperatures reached 35°C feed intake was reduced by 40%. 
Ruminal concentrations of acetate, lactate and total volatile 



fatty acids (VFA) peaked at one hour after feeding under 
hot temperatures and at two hours under low temperatures 
(13°-29°C). However, the rate of decline of acetate and 
total VFA concentrations was much slower at hot tempera- 
tures. The authors suggested an earlier availability of 
metabolites under hot temperatures with acetate playing a 
major role in the regul ation 'of intake. These results, 
and others (Ragsdale et al . , 1950, 1953; Worstell and Brody, 
1953; Lampkin and Quarterman, 1962), indicate that a ther- 
mostatic regulation of feed intake in ruminants is a re- 
sponse to environmental temperature rather than to heat of 
metabolism of ingested nutrients. 



Lipostatic regulation 

Fatty acids . Baile (1968) suggested that some para- 
meter of lipid depot level might play an important role in 
long-term regulation of energy balance since the lipid 
depot represents the largest source of body energy in the 
normal adult. Kennedy (1961) postulated that the size of 
the adipose tissue mass could signal the hypothalamic nuclei 
and that the concentration of plasma lipids conveyed the 
message, provided that the concentration was related to the 
size of the fat depots. Seoane, Warner and Seoane (1972) 
found that a decrease in lipid mobilization was associated 
with a decrease in voluntary energy intake, and that plasma 
free fatty acids (FFA) may be involved with the regulation 



10 



of feed intake. These metabolites, products of intracellu- 
lar hydrolysis of triglycerides, are transported to muscle 
tissue during exercise and to most tissues during fasting 
(Fredrickson et al . , 1967a, b; Lehninger, 1970). Their 
release from fat depots is normally stimulated by epi- 
nephrine, glucagon, growth hormone and sympathetic nervous 
system, while insulin exerts an opposite effect (Guyton, 
1971; Havel, 1965; Winegrad, 1962). 

In humans (Van Itallic and Hashim, 1960), FFA have 
been indicative of nutritional status, and their level was 
negatively correlated with arteri o- venous differences in 
blood glucose. In non-ruminants, blood FFA increase between 
meals and decrease soon after eating is initiated (Fredrick- 
son et al . , 1967c; Walker and Remley, 1970). Similar obser- 
vations have been reported in ruminants. Ruminants under 
nutritional stress, e.g., high milk production, show ele- 
vated plasma FFA (Radloff et al . , 1956). According to 
Thye, Warner and Miller (1970), FFA were the best single 
predictor of subsequent feed intake of lactating ewes on 
a schedule of two 3-hour feedings per day. Baile (1971) 
indicated, however, that although FFA increase and decrease 
with feeding behavior and energy balance there is little 
evidence that they affect either. Baumgardt (1970) stated 
that FFA levels may provide an indicator of long-term energy 
status even if FFA p_er s_e are not the feedback metabolite. 



n 



There is a relationship between plasma FFA and rumen 
VFA production (Trenkle, 1970; Trenkle and Kuhlemeier, 1966). 
Wethers were fasted for 48 hours and then various metabolites 
were injected into the rumen with the following results: 
a) acetate had no effect on FFA; b) propionate caused an in- 
crease in blood glucose, followed by a decrease in FFA after 
one hour; c) butyrate caused a depression in FFA that lasted 
two hours; and d) glucose depressed FFA. The authors sug- 
gested that FFA levels are high when liver gl uconeogenesi s 
is low due to low availability of propionate in the portal 
vein. Conversely, a low FFA level may indicate an increased 
rate of glucose uptake by tissue caused by an increased pro- 
pionate absorption from the rumen and subsequent gluconeo- 
genesis. Trenkle (1970) demonstrated that intravenous in- 
jections of propionate or butyrate raised plasma insulin 
levels within 15 minutes, which coincided with lowered plasma 
FFA levels. These results indicate that changes in plasma 
FFA levels after the initiation of a meal are primarily in 
response to increased absorption of propionate accompanied 
by an increased gl uconeogenesi s in the liver (Church, 1971). 
Tnese authors suggest that the liver must sense these changes, and 
via some unknown mechanism, signal the brain to reduce food 
intake . 

Prostaglandins . An additional group of compounds 
related to lipids, the prostaglandins (PG), may have a role 
in the control of feed intake since they are released from 



12 



adipose tissue upon neural- or adrenergic stimulation. These 
compounds are known to produce strong physiological changes 
in several tissues and organs of the body including changes 
in glucose metabolism and lipogenesis (Bergstrom et- al . , 
1968). Blood levels of PG are known to increase during 
satiated conditions but decrease during fasting (Greaves 
et al . , 1972). Recently, the role of PG in neural trans- 
mission as feedbacks from adipose tissue to the CNS for the 
maintenance of energetic equilibrium has been investigated 
(Baile et al . , 1973, 1974). The i njection of PGE-, into the 
anterior and medial hypothalamus caused a reduction in spon- 
taneous feeding, whereas PGE ] injected into the more lateral 
loci induced feeding. 

Hormones 

Hervey (1969) postulated a mechanism for the lipo- 
static hypothesis which involved a steroid-like hormone 
that may act on the dilution principle to provide communi- 
cation between adipose tissue and the CHS. An energy- 
depleted animal may decrease its fat depots causing an in- 
r-ease in concentration of the factor which, in turn, in- 
creases intake by either inhibiting the VMM or stimulating 
the LH (Hervey, 1969). The author suggested that progeste- 
rone may fulfil these requirements. 

In rats, progesterone caused increased feed intake 
and increased fat deposition during early pregnancy (Dewar, 
1962; Galleti and Klopper, 1964; Hervey and Hervey, 1964). 



13 



Changes in progesterone and estrogen secretion increased 
body weight and feed intake during pregnancy and pseudo- 
pregnancy (Wade and Zucker, 1970). In the ovari ectomi zed 
rat, feed intake and. weight increased as. estrogen and pro- 
gesterone blood levels decreased (Kakolewski et al . , 1968). 

Melengestrol acetate, a synthetic progestin, has 
increased rate of gain in heifers (Bloss et al . , 1966) and 
ewe lambs (O'Brien and Miller, 1967). In some cases it 
significantly increased feed intake possibly by suppressing 
estrogen secretion (O'Brien et al . , 1968; O'Brien and 
Miller, 1967). Baile (1971) suggested that the decreased 
feed intake observed in late pregnancy in cows and ewes 
might be caused by the placental secretion of estrogen. 

Growth hormone has been postulated to stimulate 
feeding during energy depletion in non- rumi nants (Hunter 
and Regal, 1966) but not in ruminants (Davis et al . , 1970a, 
b; McAtee and Trenkle, 1971). The effects of diethylstil- 
bestrol in ruminants are similar to those of growth hor- 
mone, and the synthetic estrogen may induce secretion of 
endogenous growth hormone (Davis et al . , 1970b; Trenkle, 
1970). Diethyl sti Ibestrol increases feed intake in cattle 
(Davey and Wellington, 1959; Dinusson et al . , 1950; Oltjen 
et al . , 1965) and growth hormone in rats (Kennedy and Mitra, 
1963). Nevertheless, there is no evidence in the literature 
that growth hormone is a feedback signal for energy balance 
under normal conditions (Baile, 1971; Baile and Mayer, 1970). 



14 



Humoral factor 

A humoral factor related to appetite has been ob- 
served in non-ruminants (Hervey, 1959; Flemming, 1969) and 
in ruminants (Baile, 1971). Hervey (1959) and Flemming 
(1969) demonstrated that changes in the energy balance of 
one member of a pair of parabiotic rats can affect body 
weight and the food intake of the other. The author postu- 
lated that the blood concentration of the factor involved 
would decline as fat accumulated in the body and as a re- 
sult feed intake would decrease. Davis et al . (1969) ex- 
changed the blood of rats fasted 24 hr with that of rats 
fed a_d libitum . Under these conditions, the fasted rats, 
upon feeding, ate less than when their blood was exchanged 
with that of other fasted rats. Baile (1971) demonstrated 
a factor in the plasma of satiated goats or sheep that 
depressed food intake in rats. The factor which decreased 
feed intake appeared to be partly related to the condition 
of the fat depots, i.e., the factor disappeared after 48 
hours of fast in goats in "good" condition but "fat" sheep 
tended to retain the factor much longer (Baile, 1971). 
Seoane (1971) and Seoane and Warner (1971) demonstrated a 
depression in the intake of hungry sheep during cross cir- 
culation with satiated animals. An increase in the intake 
of satiated sheep occurred when blood was exchanged with 
hungry sheep (Seoane et al . , 1972a). The nature of these 
factors and their mode of action are unknown. 



15 



Amino acids and minerals 

Since the effects of amino acids (AA) metabolism on 
feed intake in non-ruminants and ruminants have been re- 
viewed (Jones, 1972), only major effects will be discussed 
here. Plasma AA levels in sheep declined for a few hours 
after feeding and then increased to maximum levels 24 hr 
post-feeding (Theurer et al . , 1966). Baile and Martin 
(1971) studied the effect of intravenous injections of 
several AA to sheep. Alanine, glycine or lysine depressed 
feed intake (12-30%), but only when plasma levels were 
abnormally high. Purser et al . (1966) considered it to be 
unlikely that meal size is controlled by absorbed AA since 
they are mainly absorbed from the small intestine hours 
after ingestion of food. 

The effects of macro- and micro-mineral elements 
upon the health and productive- efficiency of livestock has 
been extensively studied. Deficiencies of many of the min- 
eral elements, including calcium (Underwood, 1962), phos- 
phorus (Preston and Pfander, 1964), magnesium (Chicco e_t 
aj_. , 1973), potassium (Telle et al . , 1964), sodium chloride 
(N.R.C., 1963), cobalt (Underwood, 1962), copper (Underwood, 
1962) and zinc (Miller etal . , 1966), are known to depress 
appetite and feed intake. 

Seoane and Baile (1973), and Seoane et al . (1975) 
studied the effects of various ions on hypothalamic control 
of feeding. Injection of Ca into the cerebrospinal fluid 



16 



caused feeding, while Na decreased spontaneous feeding in 
sheep. In similar doses to Ca , Mg also caused feeding, 
while K at much lower doses caused feed depression similar 

to that of Na . Since Na depressed the Ca -elicited 

++ + 
feeding, the authors postulated that a Ca :Na ratio in 

the hypothalamus may control feeding or may play an impor- 
tant role in the maintenance of energy balance. Chicco, 
Ammerman and Loggins (1973) reported significant correla- 
tions between animal age, plasma Mg levels and voluntary 
intake. When plasma Mg decreased, voluntary feed intake 
was reduced, especially in older animals perhaps due to a 
lower rate of Mg mobilization. 



Rumen metabol i tes 

The VFA are an important energy source for ruminants 
and show several characteristics that qualify them as com- 
ponents of a feed intake regulatory system, namely: (a) 
they are produced in the forestomachs from the fermentation 
of carbohydrates; (b) their rate of production, concentra- 
tion and absorption change rapidly with feeding behavior; 
did (c) they possess an important characteristic of a feed- 
back mechanism in that they cause the appropriate response 
when introduced into the system (Baile, 1968). Intrajugular 
infusions of VFA have shown variable responses (Dowden and 
Jacobson, 1960; Holder, 1963) while intraruminal injections 
decreased feed intake of cattle (Montgomery et a] . , 1963; 



17 



R ook et al . , 1960; Simkins et al . , 1965), sheep (Baile and 
Pfander, 1966; Ulyatt, 1965), and goats (Baile and Mayer, 
1967; Baile and Mayer, 1968b). Of the major VFA studied 
by Ulyatt (1965), acetate, infused i ntrarumi naly , most 
closely fulfilled the requirements of a feedback metabolite 
because of its presence in significant amounts in blood 
leaving the liver. Holder (1963) found, however, no effect 
on consumption of a single meal due to intra jugular infu- 
sions of sodium acetate which produced normal to high blood 
acetate levels. 

Baile and Mayer (1970) conducted detailed studies of 
the intake response to infusions of VFA to various sites 
and of the location of receptors. In summary, their evi- 
dence suggests the following: 

a) Intraruminal injections of acetate, in contrast 
to intravenous injections, caused a decreased feed intake 
indicating that blood acetate concentration is not likely 
to be the stimulus causing the inhibition of eating (Baile 
and Mayer, 1968b). No evidence for a brain receptor sensi- 
tive to acetate has been reported (Baile and Mahoney, 1967). 

b) Acetate and propionate are important controlling 
metabolites, but butyrate is not likely to be involved in 
chemostatic intake control (Baile and Mayer, 1969). Intra- 
ruminal injections of acetate and propionate, or a mixture 
of VFA, decreased digestible energy intake. Butyrate, how- 
ever, was considerably less effective in depressing intake. 



18 



Egan (1966) found that when long-term infusions were used, 
acetic acid was a more effective inhibitor than propionic 
acid. 

c) Changes in rumen fluid concentrations of acetate 
or propionate activate receptors in the rumen wall, which 
probably are most active in the dorsal sac of the rumen 
(Baile and Mayer, 1968b, 1969; Baile and McLaughlin, 1970). 
Application of a local anaesthetic to the rumen wall par- 
tially eliminated the feeding response to acetate injections 
(Baile and Martin, 1971). Propionate, also effective in 
reducing feed intake, may be sensed by similar receptors 
and by receptors located in the portal system (Baile, 
1969). Small doses (20 Mmoles as sodium salt, per meal) 
of propionate injected into the ruminal veins during meals 
reduced feed intake more than injections into the mesenteric, 
portal, or jugular veins, carotid artery or the ruminoreti- 
culum (Baile and Mayer, 1970; Baile and McLaughlin, 1970). 



Ruminal distention 

The bulky and fibrous nature that characterizes most 
:f the straws, native pastures, and tropical forages often 
results in the rumen being filled to capacity before enough 
food is consumed to meet nutrient requirements for maximum 
production. With this type of food, the ruminal distention, 
or gastrointestinal fill, has been suggested to act as the 
short-term control mechanism for feed intake (Montgomery and 
Baumgardt , 1 965a ,b ) . 



19 



Classical studies of the regulation of voluntary in- 
take of forages have been conducted by various groups of 
researchers who concluded that the amount of forage eaten 
by the animal depends upon (a) the capacity of the rumen, 
(b) the rate of food breakdown, and (c) the rate of passage 
of undigested food residues through the digestive tract 
(Blaxter et a! . , 1961; Campling, 1970; Crampton et al . . 
1960). 

The importance of bulk and its associated distention 
of the rumen was tested by Campling and Balch (1961) who 
found that placement of large water bladders in the rumen 
for 10 to 14 days resulted in a reduced voluntary intake of 
hay equivalent to 24 grams of hay per kilogram of water. 
Injecting water into the reticul o-rumen during a meal did 
not affect voluntary intake (Baile and Mayer, 1967, 1970). 
However, the addition of digesta consisting of recently 
ingested hay to the rumen of cows during a meal caused an 
immediate decrease in hay intake (Balch arid Campling, 1962). 
Several experiments have been reported in which rations have 
been diluted with inert diluents (Weston, 1966; Carr and 
Jacobson, 1967; Boling et al , , 1967; Dinius and Baumgardt, 
1970). In general, results from these experiments show that 
particles of a size that will pass out of the rumen are not 
likely to restrict intake. However, when inert plastic or 
sawdust accumulated in the reti cul o-rumen (Boling et al . , 
1969; Welch, 1967; Weston, 1966), feed consumption of hay 



20 



or mixed ration was reduced considerably, indicating that 
physical factors were' restri cti ng intake . 

Blaxter et aj . (1961) estimated that the dry matter 
contents were the same in the digestive tract of sheep at 
the end of a meal of three different quality roughages 
offered freely. This suggested that the amount eaten was 
determined by the capacity of the digestive tract. The 
authors concluded that sheep eat to constant distention of 
their digestive tract as determined by rate of passage of 
feed and digestibility and this concept was confirmed by 
Ulyatt et al . (1967). Campling et al . (1961) and Freer and 
Campling (1963) measured the weight of rumen digesta and 
showed that eating of hay ceased when the reticulum contained 
constant amounts of dry matter. The quantity of roughage 
eaten was proportional to its rate of disappearance from the 
reticul o-rumen . Slow disappearance was associated with slow 
rate of passage combined with low digestibility. 

The addition of urea to the reti cul o-rumen of cows 
offered oatstraw raised digestibility by 18%, decreased food 
retention time in the rumen, and increased voluntary intake 
by 40% (Campling et al . , 1962). Positive relationships be- 
tween digestibility and intake of roughages have been reported 
(Blaxter and Wilson, 1962; Conrad et al . , 1964). The in- 
creased voluntary intake resulting from the addition of ni- 
trogen to low quality roughages has been attributed to an 
increased microbial cellulolytic activity and increased rate 



21 



of breakdown, absorption and passage of undigested residues 
to the lower intestinal tract. Egan (1965) and Weston 

(1967) indicated that the intake response to supplemental 
nitrogen may be also due to the improved protein status 
of the animal . 

Hungate (1966), Van Soest (1965, 1968) and Weston 

(1968) emphasized that the rate of disappearance of digesta 
from the reti cul o-rumen depends primarily on its rate of 
breakdown, which in turn is a function of the chemical and 
physical composition of the roughage consumed. Soluble 
carbohydrates and protein are digested faster by the micro- 
organisms than structural components (Van Soest, 1965; 
Weston, 1968). Consequently, as the proportion of struc- 
tural carbohydrates in a forage increases, the amount of 
time required for physical breakdown increases, and the 
rate of passage and intake decreases. 

Troelsen and Campbell (1968) indicated that rate of 
breakdown and rate of passage of undigested residues from 
the rumen depends on the rate of degradation into particles 
small enough to pass out of the reticulum. Means of improv- 
ing the rate of breakdown and intake of low-quality rough- 
ages include the addition of nitrogenous compounds (Campling 
et al . , 1962; Hemsley and Moir, 1963; Houser, 1970; Ventura 
et al . , 1975), certain minerals (Blaxter, 1962), and by 
grinding and pelleting the forage (Campling and Freer, 1966; 
Minson, 1963). However, rate of breakdown in the rumen may 






22 



depend not only on the amount of structural carbohydrates in 
a forage hut also on the physical organization of molecules 
within the plant cell walls (Bailey and Jones, 1971). The 
physico-chemical structure of the cell wall is important in 
determining the biodegradabi 1 i ty of the component parts of the 
structure (Van Soest, 1968). A better understanding of these 
aspects is being pursued thru histochemi cal studies of the 
.microanatomy of sub-tropical and tropical grasses (de la 
Torre, 1974; Moore and Mott, 1973). 

It is evident that physical factors are important 
in limiting the voluntary intake of forage diets. Limita- 
tions are imposed by the capacity of the reti cul o- rumen , but 
the primary factor determining the intake of roughages with 
less than 65-70% digestibility is the rate of its degrada- 
tion in the rumen. The signal controlling the cessation of 
eating presumably arises from distention of the reticulo- 
rumen (Campling, 1970), yet the neural basis of this mecha- 
nism is not clearly understood. Stretch and tension recep- 
tors have been located in the rumen wall (Bell, 1961; 
Comline and Titchen, 1961) and in the reti cul o- rumen (Iggo 
and Leek, 1970; Kay, 1963; Leek, 1969), however, the exact 
nature and location of the sensory nerve endings in the 
reti cul o-rumen have not been reported (Campling, 1970). 

Baile (1971) considered it to be quite possible that 
gastrodistention acts as a limiting component to prevent 
severe dilation of the reti cul o- rumen when a bulky diet is 






23 



being consumed, but they are not important when a normal 
energy balance is maintained. Certain specific circumstances 
related to the physiological status of the animal (Campling, 
1970; Moir, 1970) and/or metabolic conditions within the 
animal, particularly protein status (Egan, 1965, 1970), may 
override the distention mechanism or allow resetting of the 
distention mechanism at a different level. A greater capa- 
city for roughage intake has been observed also during lac- 
tation (Mowatt, 1963; Tulloh, 1966). 

Integration of Physical and Chemostatic Theories 

The relative importance of various intake regulatory 
mechanisms changes at some undefined point with increasing 
digestible (DE) energy concentration in the ration (Baum- 
gardt, 1970). This was first expressed on a quantitative 
basis by Conrad et al . (1964) and by Montgomery and Baum- 
gardt (1965a, b). From their work it became evident that 
feed intake, and DE intake, are restricted by physical 
means with feeds of low nutritive value and by chemostatic 
(metabolic or physiological) mechanisms with feeds of 
higher nutritive values. It also became apparent that the 
physical form of diet fed (long, ground or pelleted) and 
the physiological status of the animal affects the point 
at which feed intake regulation changed from physical to 
chemostatic mechanisms. In general, in experiments where 
adult ruminants have been offered roughage containing 






24 



adequate levels of protein, physical control of intake 
appears to cease in the range of 65 to 70 percent dry matter 
digestibility (DMD) (Blaxter et a l . , 1961; Conrad et a l . , 
1964; Montgomery and Baumgardt, 1965a, b; Dinius and Baum- 
gardt, 1970). 

Conrad et al . (1964) associated voluntary intake 
with body weight and feed digestibility in lactating dairy 
cows fed rations ranging from 52 to 80 percent DMD. Their 
results indicated that the most important factors regulat- 
ing feed intake at low digestibility (DMD < 66%) were: 
body weight (which reflected roughage capacity of the ani- 
mal), undigested residue excreted per unit body weight per 
day (which reflected rate of passage), and DMD. At higher 
digestibilities (DMD > 66%) intake appeared to be dependent 
on metabolic size, level of production and DMD. Signifi- 
cant positive relationships between intake and digestible 
nutrient concentration have been reported before (Blaxter, 
Wainman and Wilson, 1961; Blaxter and Wilson, 1962). How- 
ever, it should be pointed out that when a wide group of 
forages is considered, intake and digestibility are not 
often highly correlated (Moore and Mott, 1973). 

Dinius and Baumgardt (1970) showed that intakes by 
mature sheep fed pelleted rations varying in energy concen- 
tration increased until the ration contained approximately 
2.5 kcal DE/g (DMD about 56%) and then declined with in- 
creasing DE concentration. Jones (1972) graphically 






25 

summarized most of the data published on this aspect. With 
the exception of lactating dairy cows (Conrad et al . , 1964), 
ruminants increase their intake of DM and DE up to a diet 
DE concentration of about 2.5 kcal/g. Thereafter, DM intake 
declines and DE intake remains nearly constant. Jones (1972) 
concluded that the primary determinant controlling intake 
of roughages with less than 2.5 to 3.0 kcal DE/g would be 
digestion in the reticul o-rumen. 

Effects of Animal Characteristics on 
Voluntary Intake 

The energy requirement of an animal varies with 
factors such as age, body size, level of production and pre- 
vious nutrition. Traditionally, the requirement for energy 
has been computed as the amount of energy required for main- 
tenance with an additional allowance for production. In 
general, a healthy animal will attempt to satisfy its di- 
gestible energy requirement for maximum production through 
changes in its voluntary feed intake. 

Body Size and Age 

Energy requirements for maintenance are largely deter- 
mined by the body size and age of the animal. Langlands and 
Sutherland (1968) demonstrated that the maintenance net energy 
(NE) requirements of sheep kept under thermoneutral conditions 






26 



7 5 
were more proportional to metabolic body size (W/ ) than 

to body weight. Weston and Hogan (1973) calculated perti- 
nent data from various sources (Block and Boiling, 1951; 
Corbett, 1968; Graham, 1966; Langlands and Sutherland, 
1968) and indicated that the maintenance NE requirement 
per unit of metabolic body size diminished progressively 
with age until the animal reached 2 to 3 years of age. 
For example, the maintenance NE requirement of 26 kg Border 
Leicester x Merino crossbred sheep about 100 days old was 
the same (1000 kcal/day) as an adult sheep weighing 40 kg 
(Weston and Hogan, 1973). Ritzman and Colovos (1943) found 
that the maintenance DE requirement per W,\ /day of cattle 
declined from 172 kcal at 8 days of age to approximately 
100 kcal at one year of age, and to 81-85 kcal when they 
were about 2-3 years of age. 

Under practical conditions, the effects of animal 
exercise on maintenance requirements must be considered. 
Although limited data have been reported on this aspect, 
grazing sheep (Grimes, 1965) and cattle (Hancock, 1952; 
Huffman, 1959) require approximately 20-70% more energy 
for maintenance than stall-fed animals. 

Holmes et al . (1961) studied the influence of size 
on intake of growing and mature cattle grazing a mixture 
of perennial ryegrass ( Lolium perenne ) and white clover 
( Trifolium repens ). Mean daily organic matter (0M) intake 
estimates were 10.6 kg for cows (592 kg live wight), 9.4 kg 






27 



for heifers (357 kg live weight) and 6.5 kg for calves 
(205 kg live weight). Relative to live weights, however, 
these values were: 18.0, 26.4, and 31.8 grams/kg live 
weight for cows, heifers and calves, respectively. The 
calves selected a diet of higher digestibility than cows, 
and the mean OM digestibility was 69.5 percent. 

A classical study on the influence of age and weight 
of sheep on their intake of forage was conducted by 
Hadji pier is et al . (1965). Adult (5 years old), yearling 
(16-20 months old) and lamb (4-8 months old) wethers grazed 
a five acre pasture of perennial ryegrass-whi te clover for 
three periods of 35 days each. Crude protein content of 
the forage DM during those periods ranged from 15.5 to 
17.5%, with an OM digestibility of 68-74%. No significant 
differences in the OM digestibility due to age was found. 
There was, however, a progressive increase in intake with 
age. The estimated digestible organic matter (DOM) intakes 
showed that the adults consumed 1.2 to 1.4 times more for- 
age than the lambs. In terms of absolute values, intake of 
DOM for the adult, yearling and lamb wethers was 1360, 1300 
and 1060 g per day, respecti vely . However, when intake was 
expressed relative to body weight, the yearlings (16-20 
months old) showed the highest intake of DOM (23 ±1.0 g/kg 
body weight) while the adults were lowest (14+1.3) and 
lambs were intermediate ( 22 . 7 ± 1 . 0) but not different from 
yearlings. According to the authors, the higher intake per 






23 



kg body weight was due to a higher fasting metabolism of 
the younger animals, as reported by Blaxter (1962). However, 
no attempt was made to partition the variance in intake 
between body weight and age. Holmes et al . (1961) found 
that adult cows consumed about 1.6 times the quantity of 
DOM consumed by growing calves 11 months old at physiolog- 
ical stages of development comparable to that of lambs and 
adul t sheep. 

Langlands (1968) found no relationship between in- 
take and live weight of grazing sheep. In fact, within a 
breed, intake was more closely related to age than to 
live weight. Quadratic relationships between DOM intake 
and age were reported. In general, intake of DOM increased 
with age, reached a maximum value at approximately 33 
months, and declined thereafter. The lack of relationship 
between intake and live weight may have been due to differ- 
ences in pasture availability. Drought conditions prevailed 
during the experiment and there was a decline in the mean 
live weights of the animals, particularly in the older group 
of sheep. Under such circumstances, therefore, potential 
differences in intake may have been masked by low forage 
avai 1 abi 1 i ty . 

Ag e, Size and Diet Interaction 

The effects of bulk density and feed digestibility 
(diet dilution effect) on the voluntary intake of young 






29 



animals have been reported in various species of animals 
(Hill and Dansky, 1954; Leng and Brett, 1966; Owen and 
Ridgman, 1968; Troelsen and Bell, 1963). When concentrate 
diets were diluted with fibrous materials, lambs increased 
their voluntary intakes in order to meet energy demands 
(Owen et al . , 1967; Woods and Rhodes, 1962). Dilution 
with roughage was achieved by grinding and pelleting the 
entire ration. The reduction in particle size, as discussed 
earlier, increases rate of passage and reduces the filling 
effect. Initial work by Andrews et al . (1969) on the effect 
of diet dilution on voluntary intake of lambs, led these 
authors to suggest that as lambs mature they increase their 
ability to achieve similar digestible DM (DMD) intakes with 
diets of varying bulk density and digestibility. Later ex- 
periments (Andrews and Orskov, 1970) confirmed previous 
reports that grinding the diluent removed the factor inhib- 
iting compensatory intake with young lambs and enabled simi- 
lar DMD intakes to be achieved. As live weight of the grow- 
ing lambs increased, intakes of the more bulky diet (whole 
oats), while initially lower than those of a concentrate 
diet (barley), increased faster and were ultimately higher 
(Andrews and Orskov, 1970). The inhibitory effect on in- 
take of the whole oat diet seemed to disappear between live 
weights of 30 and 40 kg. 

The point between bulk limitation of food intake and 
energy regulation remains to be defined. Dinius and Baumgardt 



30 



(1970) and Baumgardt and Peterson (1971) pelleted concen- 
trate diets diluted with oak sawdust, kaolin and verxite to 
obtain various concentrations of DE. In mature sheep, DM 
intake per unit of metabolic weight increased as the DE per 
gram of feed increased to approximately 2.47 kcal. Above 
this DE concentration, intake of DM declined. Young grow- 
ing lambs (11 weeks old) showed a higher threshold point of 
DE intake regulation. A basal concentrate diet was diluted 
20, 30, 40, and 50% by weight with mixed oak sawdust to 
provide DE concentrations ranging from 2.89 to 1.86 kcal/g, 
and DMD ranging from 65 to 42%. At 65% DMD, which corre- 
sponded to a caloric value of 2.9 kcal/g, intake values 
provided the best estimate of the point at which these 
lambs attempted to regulate DE intake. Average DE intake 
in this treatment was 266 kcal per kg of metabolic weight, 
and is similar to the values obtained for young rats 
(Baumgardt and Peterson, 1971) but higher than for mature 
wethers (206 kcal per kg of metabolic weight) (Dinius and 
Baumgardt, 1970). Lambs consuming the 40 and 50% diluted 
diets were unable to meet DE requirements for production. 
This restriction of DE intake was more evident in early 
periods of the experiment, but a general trend for DM in- 
take to increase with age was observed with lambs consuming 
the 40 and 50% diluted diets. 

These results indicate that younger animals show a 
higher feed intake relative to body size because of higher 






31 



metabolic rate. The maximum DE intake per unit of metabolic. 
weight, or the point at which DE intake is regulated by 
chemostatic controls,, tends to decrease as animals mature. 
If the diet contains a high caloric density (i.e., high 
DE/g), -young animals will show their potential maximum DE 
intake, whereas if it is low in DE/g feed intake will be 
limited by rumen fill which is in close relationship to the 
size of the digestive tract and the size of the animal 
(Balch and Campling, 1962). 

Changing the physical form of the diet (i.e., grind- 
ing and pelleting) undoubtly eliminates some of the factors 
that regulate intake of feed low in digestibility, particu- 
larly for young animals. The magnitude of this effect may 
vary not only with age and size within a species, but also 
between species. Greenhalgh and Reid (1973) studied the 
effects of pelleting diets on the intake and digestibility 
in sheep and cattle at various physiological ages (6, 18, 
and 36 months). Pooled values indicated that young animals 
(6 months old) ate less of long forage than old (68 vs. 
72 grams per kg metabolic weight), but when the forage was 
pelleted young animals were able to consume larger amounts 
than older animals (94 vs. 86 g/kg metabolic weight per 
day). These values represented a 38 and 20 percent increase 
in the feed intake of the young and old animals, respectively 
Differences between species agreed with other reports, i.e., 
cattle ate more feed, regardless of physical form, per unit 






32 



of metabolic weight. Nevertheless, pelleting improved in- 
take more in sheep (45%) than in cattle (11%). As expected, 
the digestibility of the DM was reduced by pelleting. Age 
had no effect on digestibility, however, but favored slightly 
(< 2% units) the middle age (18 months) group of animals. 

Rate of Production 

Among the factors that most influence energy require- 
ments is the productive status of an animal. For example, 
growth may be stimulated in ruminants by d iethyl sti 1 bestrol 
implantation (Davey and Wellington, 1959; Dinusson et a] . , 
1950). The physiological response to this stimulant in 
steers fed al 1 -concentrate diets was shown by Oltjen et al . 
(1965) to be an increase in body weight by about 20 percent 
while feed intake increased about 6 percent. Similar effects 
have also been reported with forage-fed steers (Quinn et al . , 
1958). 

The increased energy requirement of lactation is gen- 
erally accompanied by an increased feed intake. Comparison 
of monozygotic twins fed hay or concentrates (Campling, 
1965) and grass (Hutton et al . , 1954) showed that lactating 
cows ate more than no n -lactating controls. Positive corre- 
lations between milk yield and intake have been reported 
(Forbes, 1970) although it was not clear which was the caus- 
ative factor. Conrad et al . (1964) commented that when 
roughages were fed, milk production more likely depended on 






33 



the amount of metabol izabl e energy (ME) the animal obtained 
from the feed. With concentrate diets, however, energy in- 
take responded to requirements, and milk energy output af- 
fected feed intake (Conrad et a! . , 1964; Forbes, 1970). 

Curran and Holmes (1970) and Curran et al . (1970) 
found that at any particular stage of lactation milk yield 
was often highly correlated with feed intake, a relationship 
that also held between total milk yield and total feed eaten 
in a whole lactation period. Ewes under many conditions 
also increase feed intake during lactation (Arnold, 1970; 
Cook et al . , 1961; Coop and Drew, 1963; Hadjipieris and 
Holmes, 1966). Flatt and Coppock (1963) reviewed the ME 
requirements of the lactating ruminant, and the energetic 
efficiency of milk production under a variety of conditions. 
Baumgardt (1970) summarized data from 15 experiments where 
DE intake had been related to milk yield and/or to live 
weight gains. The data suggest a level of intake control 
between 200 and 300 kcal of DE intake per kg of metabolic 
weight for growth and fattening, and between 350 and 500 
kcal for lactation (Baumgardt, 1970). 

Fatness 



Several theories and much data have suggested that 
the amount of adipose tissue stored in the body may play an 
important role as a feedback mechanism in the regulation of 



34 



energy intake. In general, adult cattle and sheep eat less 
when fat than when thin (Church, 1971; Ferguson, 1956; 
Mather, 1959). Tayl er (1959) reported inverse relations 
between weight of internal fat and the amount of forage 
eaten by grazing cattle. Bines et al . (1969) showed that 
thin non-pregnant, non-1 actati ng cows ate approximately 
31 percent more hay and 23 percent more concentrates than 
the same animals when fat. There may be physical limita- 
tions due to accumulation of adipose tissue in the abdomi- 
nal cavity, reducing its capacity and limiting intake of 
roughage by the animal (Bines et al . , 1969; Forbes, 1969; 
Tayler, 1959). Bines e t a 1 . (1969) did not consider this 
a simple physical regulatory mechanism, however, since con- 
centrate intake was reduced in fat animals even though the 
rumen was not filled to capacity. It was concluded that 
intake regulation was more metabolic in nature, allowing 
the thin animals to eat more of the diet. Further metabolic 
studies (Bines, 1971) indicated there was a faster utiliza- 
tion of lipogenic substrates by thin cows than by fat cows, 
as evidenced by a lower concentration of these substrates 
in the blood of thin animals. 

In sheep, fatness appears to restrict feed intake as 
in cattle. Graham (1969) observed that mature wethers con- 
sumed less food when their fat content reached 30 percent 
of live weight. The most obvious effect of fatness was loss 
of appetite. Foot (1972) reported similar results with 






35 



Scottish Blackface non-pregnant ewes grouped into two cate- 
gories: "fat" (more than 27% body fat) and "thin" (less 
than 20% body fat). After a six week period, the mean daily 
DM intakes by the thin and fat sheep were 106 and 68 g per 
kg of metabolic weight, respectively. 

Donnelly et al . (1974) considered, however, that 
under practical grazing conditions extreme differences in 
fatness were not likely to be encountered. Within a mean 
body weight range of 28 to 37 kg, imposed by grazing abun- 
dant or sparse pastures, the energy status (fatness) of the 
animals had no effect on the intake of pasture or on the 
time spent grazing. Compensatory gains occurred when sheep 
were moved from sparse to abundant pastures, but much of 
this gain was water. Compensatory growth has been observed 
repeatedly in grazing animals (Alexander and Williams, 
1973; Bohman, 1955; Crichton et al . , 1959; Donald and Allden, 
1959) and it seems to be associated with greater forage in- 
take by the previously undernourished animals (Allden and 
Scott Young, 1964). 

Exponents Relating Body Weight to Nutrient Intak e 



The basal metabolism of animals has been used exten- 
sively as a reference base for computing animal requirements 
for maintenance, gestation, lactation, growth, and for esti- 
mating the feeding level for meeting those requirements. 



36 



This aspect of animal research traces .to 1883 when Max 
Rubner reported that the basal metabolism in adult dogs 
diminished with the size of the animal, but if expressed 
per unit of surface area, then all dogs produced the same 
amount of heat (Blaxter, 1962). 

Considerable research has since been conducted on 
this subject, utilizing different species of animals. Both 
Kleiber (1932) and Brody and Procter (1932) appreciated the 
task of measuring body surface area and proposed that basal 
metabolism be related to some power of body weight. Kleiber 

(1932) provided evidence that this relationship should be 

7 5 
represented as weight to the .75 power (W ). Brody and 

coworkers (1932, 1945), in their classical studies including 

animals ranging from mice to elephants, showed a constant 

734 
ratio of basal metabolism to to" in mature animals. Brody 

(1945), and later Kleiber (1961), proved by a linear corre- 
lation between the logarithm of fasting metabolic rate and 
the logarithm of body weight that the metabolic rate of 
homeotherms, ranging from mice to cattle, is proportional 

to the .734 or .75 power of body weight. The use of meta- 

73 
bolic size (W ) thus provided a means of comparison among 

species with widely different sizes. Exceptions to the 

generalization that the basal metabolism of all homeotherms 

73 
is 70.5 kcal/W^ have been pointed out, however. Blaxter 

(1962) indicated that adult sheep and adult cattle deviate 

from this relationship considerably (±15%). The author 






37 



indicates that "the concept of metabolic size would suggest 
that the metabolism of an adult steer ten times as heavy as 
a sheep would be 5.4 times as great. In fact, the metabo- 
lism of the steer is 7.6 times as great as that of the sheep. 
Expressed another way the metabolism of adults of these two 
species varies with weight raised to a power of about 0.9 
rather than with a power of about 0.7." Differences in the 
basal metabolism between young and adult animals were also 
reported (Brody, 1945; Flatt and Coppock, 1963). 

Kleiber (1961) provided further evidence with mature 

75 

animals for the use of W* . This reference base was ac- 
cepted at the Third Symposium on Energy Metabolism as a 
standard method of expressing results of fasting metabolism 

tests for interspecies comparisons (Blaxter and Wainman, 

7 5 
1964). Since then W" has been a common, but not universal, 

reference base for expressing feed intake of animals sub- 
jected to a wide range of experimental conditions. A brief 
analysis follows of the conditions prevailing in some of 
these experiments in order to help understand the possible 
causes for the discrepancies obtained when computing the 
relationship between body weight and feed intake. 

Ivins (1959) presented original data demonstrating 
that forage intake by cattle was most closely proportional 
to body weight. MacLusky (1955) also reported a close cor- 
relation (r = .98) between the live weights of dairy cows 
and forage DM intake. Several other workers have calculated 



38 



by regression analysis the exponent of live body weight 
(reference base) which gave the best fit with their feed 
intake data (table 1). The exponent, or reference base, 
is the regression coefficient when log-j Q of intake is 
regressed on log-.* of body weight. The base varied from 
.26 to 1.0 depending on characteristics of the rations and 
the animals. Under grazing conditions the base obtained 
with cattle varied from .30 to .78 (Corbett, 1960; Corbett 
et al . , 1963; Hodgson and Wilkinson, 1967; Holmes et al . , 
1961), and from .53 to 1.0 under barn feeding conditions. 
With sheep, the base obtained has been higher (.53 to 1.01) 
than with cattle, both under grazing (Hadjipieris et al . , 
1965; Langlands et al . , 1963b) and barn feeding (Blaxter 
et al . , 1961; Greenhalgh and Reid, 1973; Langlands et al . , 
1963a). 

Col burn and Evans (1968) and Karue et al . (1971) 
have shown a wide variation in reference base. Karue ejt 
al . (1971) indicated that the reference base decreased as 
dietary energy level increased, and that in general a 
higher dietary quality was indicated by a lower reference 
base. These findings appear to agree with concepts of 
voluntary intake control as affected by digestibility. 
Conrad and Hibbs (1969) selected 67 percent Dfl digestibility 
as the point which approximately seperates physical and 
chemical control of voluntary intake. In a classical study, 
Conrad et al . (1964) demonstrated that with roughages rations 






39 



9- 
CQ 

Q 
UJ 
H 
ctf 

o 






CD 

^ — i 

LU 



9- 
Q 

O 



LU 
i<C 



o 

o 



LU 



O LU 

oi a: 

J— 

I— <c 
a: a 

<£> LU 
i — i | — - 
LU l—l 



>- LU 

O I— 
CQ 



O 

CO 

LU LU 
CO CJ 

ca =d 
o 
LU oo 
o 

2: CO 

LU => 

cc o 

LU 1 — 1 

u_ ai 
lu <c 
cr: > 



CO 



CD 

CJ 

c 
ai 
s~ 
oj 
4- 
OJ 



a-' 




CJ 


jD. 


c: 


CO 


CD 


CD 


S- 


00 +1 


0) 


to 


4- 


CQ 1- 


CL) 


jO 


a: 


' — ' 




cd 




U r— 




CD -O 




J^ rt3 




cd "p- 




+J S- 




c: n3 



V) 

3 

on 

i. 

o 

C) 

CD 





CD 




*i — 




O 




CD 




o_ 




CO 




00 


S- 


1— 


<n 


fO 


n 


4- £ 


E 


O •!- 


3 


£ 


z 


« 




ftt 




O <- 



to 
u 

'J — 
4-> 
00 

S~ 
CD 
+-> 
O 

ns 

i. 

CO 



c 
o 

•r— 

a: 





1 — 




-a 


re 




c 






res c 


-P 







CD 




s= 01 




c — - 


00 — « 


WrN 


CD r— 


enj^ vd 


E VD 


"0 1 — en 


1— CT> 


1- 1— 


O r— 


3=3*— 


ac — ' 




CD 


"5f 


CM 


O 


IO 





4..J 
CD 

£~ 

CD CO 

_Q CO 

s- ai 

O r— 

o 



+1 

t — 

10 



CO 



£ 


s: 


O 


= = 


a 


a 



CQ 



CO 



CQ 



■CO 



CQ CQ CQ 



OOO 

r— I— OJ 



CO 



O 00 

O u) >, 

4- it! JE 

00 i- +J 

Ji! DIO 

O CD E 

O >, >, 

CJ S- +-> 



CD 
S- 

3 
4-> 
I/) 

fO 

o_ 



s- 

CD 
> 

o 



co 00 
•1— 00 



c 



CD 

cu cn-p 

i- CD -r- 
CD >^JC2 

a. i~ 3b 



as 
s- 

+■> 
00 

CCS 

Cu 



LO CO 

co co 



CM LO 
CO t-v 



to o 

00 o >, 

Hi 'r- JC 

S~ co +-> 

Cn^ o 

OJ O E 

>> O -r- 

C- (J +J 



CD 

U 

~> 

4-> 

to 
fO 

CL. 



TO 

•P 
CD 

-a 

&.<-» 

res CT\ 
-ii CO 
O 01 



CO r--. 00 

•=1-1 — CM 


1 
1 


+! +1 +! 




CO CNJ WD 

r-~. r~^ oj 


CO 

LO 



Q 













CJ1 
















c 
















•r- 
















+-> 
















re 
















4-> _ 








!^; 






CO 


CO 


~ 




00 


s 




to 


X 






CO S- 





to 


s. 


O 


1 




to 


CD CD 





CD 


CD 


O 


r~. f\ 


«s 


CD 


> 4- 




> 


4- 




co co 


CO 


> 


~ T— 


>> 


r-*- 


*r— 


>> 


5 ^: 


3: 


r— 


(73 CD 


S- 


ra 


CD 


S- 


O O 





fO 


cj ^r 


-0 





JC 


•a 


CJ 


O 






CQ 



«=*■ 

C'-J 



0-1 

CO 

I 



r- ■ 
i_ 
ro ■ 



O 

en 



CJ 



c 
s. 

CQ 



CTi CM 

CT1 CO 






CO CQ 



•st 



CD 

ro O 
-C O 
OH — 

3 I 

o o 



xs 

a> 
<+- 



« 




1 — 




-0 


CO 


CDk— - 






CO 




c 


co 


JD 


4-> 








ra 


01 


CO CO 


CD. 




•!-> 






1 — 


-a co 




CD 




c 


- — * 


c: cri 


"53 - — » 


^-*>» 


C- 




fO r— 


03 ■* 


CD r— 


3 


CO 


r— *^--' 


S~ CO 


3 hv 


J3 


c 


en 


c 01 


S- CT) 


1 — 


fO 


a • 


O 1 — 


ro 1 — 





> 


res 1— 


CJ "w* 


>/ • — <* 
CD 


CJ 


LU 


_i (C 


1 1 


r«- 


«*• 




r>. 


1 


1 


Cl 













CO 
LO 



s: 



LO 



o 



c 






J 1 












4-> 






CJ 


K 




fO 




to 


*» 


«\ 


s_ 


CO 


CO 


CD 


5 


s 


CD 


O 





+J 


O 





to 



CQ 



CO 

o 



CO 

S_ 
QJ 

<D 
co 



CQ 



CO 
CO CO 


CM 
LO 


CO 



E 
i- 

ra 

CQ 



■P 

cr 
aj 

CD 

+ 1 — 

CL 
>, CX 

ea rs 

JS CO 



-o 

CJ 
4- 

E 
J_ 

rd 
CQ 



4- 
CT) 

CD 



tO "O 
CO CD 
fO Q. 

s- a. 
en o 
-a je 
S- cj 

« 

>, 

S- ra 

o -c 



T3 
GJ 



CT. 
S- 

fO 

CO 



+1 

I — ■ 

o 



o 



to 
S- 

4-> CD 

t— SZ. 

-a cd 
res 2 



o 






i 

o 

co 



co O 
CO O 

as 4- 
s- co 

cn-^: 

CD O 

>> o 
s- cj 



CL» 
S- 
3 
-M 
;/) 

res 

0- 



40 









— , 


TJ 






, — .. 


,. — % 


its 


C 






lo 


r— 


CO 


ro 


*""*»l 




to to 


CO 


LO 


- — * 


CO 


CD 


•i— CT> 


Cn 


cn 


sz cn 


-a to 


O 


i- i— 


i — 


LO i — 


cnr-~ 


C Crt 


E 


cu -^ 


>v ■ 


"O — - 


i — CTl 


ro i — 


CD 


•r- 


S- 


c 


ro i— 


* — • 


S~ 


O- • 


cu • 


res • 


JZ ■ — 


%- 


CD 


•r~ r— 


P r— 


i — • i — 


e 


o cn 


4- 


•r~3 fO 


x ro 


cd ro 


CU "O 


r— c 


CD 


-o 


(0 


C 


CD T- 


>, =5 


ck: 


ItS 4-> 


i — +-> 


ro +-> 


S~ OJ 


ro o 




rc cu 


co cu 


_J cu 


cj3 eas 


I— >- 



0) 




1 — 


r^ 


o 




X) 


i — ■ 


c 


cu to 


# 


a^ 


LO 






i- 


(8 


+1 


+1 


01 


CO 






4- 




i — 


t-» 


QJ 




X] 


cr> 


DC 




at 






O 


r— 






CU 


X! 






--^ 


ro 


^. 




ro 


•i — 


O 




4-» 


j~ 


Q 




c 


ro 





LO 

CU 
•r" 
CJ 

cu 

D. 
00 



00 

S- i— 

cu ro 

xi 4- E 

E O •!- 

=5 C 

2: < 



ro 
a- 



o 



03 
=5 
SZ 
'r 
+-> 
E 

o 



cu 



<t, 



to 
o 

■r~ 
•P 

to 

i~ 

cu 
+j 

o 

ro 

ro 

SZ 
CO 



e 

o 

-I — 

p 

IT3 



p 




LO 


ro 




a> 


-p 




cn 


to 




ro 


S- 


to 


to 


o 


s- 


3 




cu 


o 


CD 


x: 


>i — 


Cn 


+-> 


S- 


<C 


CD 
3 


> 



CO 



cn 

to 

i 

co 



r~ r— to 

i— CM r— 



+ 1 +1 +1 



i — cr> co 

co com 



a 



to 

S- CO 

a) P 

XT r— 

P 3 

cu -a 

2 ^ 



o 



ro 



LO 

o 



CO 






o 



cn 



o 



<3- CTs <*■ 


i-s 


<jLnN 


1 




o 




CO 







>> 












P 








S- 




•i" 








01 




r— 


— 


r 




> 




ro 








L0 O 




rs 






L0 


to i — 




cr 


E 




to >-> 


ro cj 






zs 




ro sz 


i- 




j_ 


•r- 


c~ 


J- -!-> 


Cn"D 




o -a 


CTl 


CJ) o 


QJ r— 


>> 


o 


CD 


•r~ 


>^ E 


>>-r- 


ro 


Q. 


E 


SZ 


CU -r- 


i- 3 


"O 








i- 4~> 

-a 


a 


CD 








CD 


i- 


4- 








4-- 


3 
4-> 


c 








c 


to 


Sw 








i- 


ro 

2_ 


ro 

CO 








ro 

DO 



<sf- 


r~- 


LO 


CO 


CO 


CD 


• 


• 


' 


+1 


+1 


+1 


LO 


LO 


! ■ 


Ch 


t^ 


O 






O CQ 



CO CO 



Q 



LO 








L0 




L0 T3 








c 


</) 


S~ CD 








■f— 


0) 


CD CU 








-- 


CD 


x: S- 








+J 


ro 


+J J3 












as 


LO 






CD 


to 


S LO 


CD 


to 




i- 


13 


Z) 


ai 


S- 


to 


•r~ 


o 


•> o 


ro 


CD 


J_ 


sz 


.(-_ 


L0 »r- 




sz 


CD 


to 


i. 


CJ s- 


*o 


-!-5 


ai 


<-, 


ro 


5 C3 


c 


CU 


j_) 


>> 


> 


cu > 


ro 


s 


to 


=£ 





CM 
CM 



CT) CO 








LO LO 








1 1 

CO r— 


1 

1 






to r~- 




CD 




i — 




CJ 




ro to 


■a 


1 — 




•r- L0 


S- 


r— 




c ro 


ro 


CD 




c s- 


-o 


a. 




cu cn 


E 


i 


-p 


S- CU 


ro 


r— 


cu 


cu >, 


+-> 


r— 


•r- 


Q. i~ 


in 


ro 


•a 


-o 


X3 






CD 


cu 






<*- 


ti- 






c 


er 






S- 


'- 






ro 


ro 






CO 


ai 







JO 

co 



i- 
o 
S- 
s-- 

O) 
T3 

s. 

ro 
•o 

ro 
■P 

LO 



+1 



-Q 



01 

to 



5- 
CU 

J= 

4-> 
O 

-a 

CD 

■p 

ro 

CJ 





01 


• 


CO 


S- 


ro 


0) 


_Q 


4-J 




-p 


CD 


ro 


« ) 


E 


C 




CD 


>, 


S- 


l- 


0) 


x^ 


q- 




cu 


II 


i~. 



Q 



*1 — 




• « 


4-'' 






T3 




5E 


x: 






C 




o 


cn 






'i — 




GJ 


"5 — ' 

CD 






to 




r — ■ 


13* 






LO 




XI 








O) 




•i — 


>5 






r— 




^ 


-a 






C 




LO 


o 






3 




CD 
CD 


CQ 






«t 




•r— 


O 






>, 




-a 


i — 






4-> 






CO 






■r~ 




ii 


o 






r-^ 






_l 




• 


•1— 




*r 


> — ^ 




>l 


^Q 




o 






4-> 


•r~ 


• 


Q 


r~* 




'i — 


p 


CJ 




JD 




i — 


to 


— 


n 






'i — 


cu 


•i— 


S- 


+ 




XI 


CD 


> 


CD 






•r" 


•i — 


o 


■P 


O 




-P 


13 




P 


JD 




to 




II 


ro 






CD 


S-. 




E 


II 




cn 


0) 


o 








-I — 


-p 




o 


CD 




-a 


•p 


* r> 


«r- 


J*£ 






ro 


CU 


E 


ro 




^. 


E 


C" 


ro 


P 




CD 




•t — 


cn 


E 




P 


o 


> 


S- 


» — I 




P 


•r" 


o 


o 






ro 


C 


ja 




o 


CD 


E 


ro 




II 


r-~ 


CO 




CO 


:i 




cn 


E 


>) 


s_ 




s: 


o 


ro 


&. 


o 


CQ 


o 


_J 


oc 


Q 


ro 


jd 


CJ 


TD 


CD 


■4- 









41 



showing a range in DM digestibility of 52 to 66 percent, 
the reference base was .99. With rations between 67 and 
80 percent DM di gesti bi 1 i ty, however , intake decreased with 
increasing digestibility, and the reference base was .73 
at peak lactation. This indicates that the intake of feeds 
with less than 67 percent digestibility is limited by body 
capacity while intake of feeds above 67 percent digesti- 
bility are limited by the metabolic ability of the animal 
to utilize digestible energy. 

Undoubtly the interpretation of the relationship 
between body size and DE intake is complex. The reference 
base as originally calculated by Brody (1945) related to 
changes in basal metabolism (and not feed capacity) with 
differences in size between mature animals of different 
species. He showed it to be inapplicable to growing ani- 
mals within a single species. Brody (1945) showed also 
that the resting metabolism reference base of growing 
Holsteins and Jersey heifers varied from .56 to .84 at 
different stages of growth. Moreover, Thonney et al . 
(19 74) provided evidence for a need to reevaluate the 
appropriate power for various species, and cautioned about 
pooling data across species-sex subclasses to develop 
single equations of fasting metabolism for all species. In 
addition, previous research has indicated that fasting 
metabolism is also affected by previous plane of nutrition 
of the animal (Marston, 1948), age (Blaxter, 1962), physio- 
logical state (Ritzman and Benedict, 1938), and environmental 



42 



temperature (Blaxter and Wainman, 1961), as well as species, 
sex and body size. 

Many of the factors affecting basal, or fasting, 
metabolism are known to affect voluntary intake also, and 
they could have been, in part, responsible, for the observed 
.variations in computed reference base values. Holmes et al . 
(1961) stated "it seems questionable whether any single 
exponent of live weight can be adapted for animals at all 
ages and live weights." From the experimental evidence 
reviewed this appears more 1 i kely to be impossible, since 
many conditions (animal and feed) and circumstances 
affecting voluntary intake are being superimposed on a sin- 
gle variable: Body Weight. Therein lies the need for 
segregating and quantifying those "other" variables. This 
dissertation has the objective of contributing to this need. 



EXPERIMENT I 
REPEATABILITY OF VARIOUS EXPRESSIONS OF FORAGE INTAKE 

In vivo trials were conducted to (1) measure the 
intake and digestibility at different ages of sheep fed 
pelleted forages differing in nutritive composition and 
(2) estimate the repeatability of various forms of ex- 
pression of voluntary intake. 

Procedure 

Experimental Design 

A series of four intake and digestibility trials 
were conducted at six months intervals during an eighteen 
month experimental period (table 2). Trials one (I) and 
three (III) were conducted in the Fall of 1972 and 1973, 
respectively, while the second (II) and fourth (IV) trials 
were carried out in the Spring of 1973 and 1974, respec- 
tively. At the initiation of the experiment (Trial I) a 
group of twenty four Suffolk x Native crossbred wethers 
were randomly assigned to three dietary treatments. The 
animals remained in the assigned treatments during suc- 
cessive trials. 



43 



44 



UJ 



c£ 
LU 
Q. 
X 
LU 



UJ 



UJ 
SL 

LU 

CD 

< 
OS 

< 



UJ 



CO 

< 



< 

I 1 



cm 



CO 
CM 



CM 



CM 

<JD 



CM 

O 



0) 

o 

LU. 



CO 



CO 



co 



CO 



OO 



co 



co 



CO CO 



CO 



CO 



CO 



co. co u_ 

O" CD" _l 

— ! DC < 





fO 


II 


> 




*i — 


CO 


4-> 


CD' 


CO 


n: 


CO 



. #\ 


o 


^-~. C7> 


C 


CSS 


O 


a 


r— 


■i— 


>-o 


+J 


QJ 


u 


s: 


fl3 




"O 





o 

-o 
o 

CD 



4- 






r3 



C 

o 



4~< 

(0 



J3 

e 

o 
o 






V) u_ 




— 


crt _l 






co <C 




o: 


S- 




en 


CT> ■" 




< 


CO <A 




i 


T3 00 




<U 


3 (O 




CD 


E t- 




■■•o 


i- CD 




S- 


CD (O 




o 


X5 "O 




UL 


3 






r- E 




jC 


(0 i- 




u 


+-> cu 




a 


(/) JD 




OJ 


113 


• 




O i— 


in 


c 


O fO 


sz 


■1— 


+J 


4J 




>, 1/1 


r: 


■J~l 


+-> to 


o 


^™ 


•i- o 


E 


ro 


r— O 




£ 


fO 


£-. 


•r~ 


= >> 


•r~ 


■r. 


CD" 4-> 




ta 


•r— 


CIS 




3: r- 


CD 


1- 


O co 


txi 


o 


—I 3 






CD- 


r— 


j- 


II 


CO 


0) 


jr 


E 


XI 


CO C7! 


•i— 


E 


cy-r- 


<r 


C3 


_j re 


<: 


s: 


— 


rsi 


CO 






45 



Dietary treatments consisted of three pelleted hays: 
a) low quality Coastal bermudagrass ( Cynodon dactyl on ) (LQB), 
containing approximately 7 percent crude protein (CP), b) 
high quality Coastal bermudagrass (HQB), with 14 percent CP, 
and c) alfalfa ( Medicago sativa ) (ALF), with 17 percent CP. 

Enough of each of these diets was purchased to last 
for the entire experimental period, and were stored in sealed 
plastic bags until fed to the experimental animals. Prelim- 
inary samples of each of these diets was obtained by random 
sub-sampling several of the stored feed bags. The samples 
were placed in plastic bottl es ,' flushed with helium gas, 
sealed and stored at -10°C until analyzed. 

Intake and Digestion Trial Procedure 

Ten days prior to the initiation of each intake and 
digestion trial the animals were treated for internal para- 
sites, and housed in group pens. One day before the begin- 
ning of the trial live weights were recorded, fecal collec- 
tion bag fitted, and each animal assigned at random to 
individual cages. The intake and digestion trials con- 
sisted of a 14-day preliminary period and a 7-day collec- 
tion period. Standard daily procedures were the same in 
each trial. All diets were offered ad li bitum , by adjust- 
ing the amount of feed offered daily so as to collect a 
refusal (oris) of approximately 250 to 300 grams from each 
animal, the feeders were thoroughly cleaned once daily 






46 



during the morning prior to feeding, and the orts weighed. 
Fecal bags were emptied in the morning and in the after- 
noon. Access to water, def 1 uori nated rock phosphate and 
trace mineralized salt was provided at all times. 

During the collection period, diets were sampled at 
each feeding, daily orts were collected, dried (50°C), and 
allowed to equilibrate with the atmosphere. Fecal mate- 
rial collected from each animal was weighed, thoroughly 
mixed, and a twenty percent aliquot stored at -10°C. At 
the termination of each trial, final weights of the animals 
were recorded, and daily diet and orts samples were pooled, 
by diet and by animal respectively, weighed to the nearest 
gram, ground to pass a 4 mm screen in a large Wiley mill, 
mixed, and a representative portion reground thru a 1 mm 
screen. Daily fecal samples were allowed to defrost, 
pooled by animal and subsequently dried at 60°C under 
forced air. The dried pooled sample was equilibrated, 
weighed, and processed in the same manner as the diet and 
orts samples. 

Laboratory Analysis 



Samples of diets, orts, and feces were anlayzed for 
dry matter (DM), organic matter (OM), and crude protein (CP) 
by A.O.A.C. (1965) analytical procedures; ash-free neutral 
detergent fiber (NDF) according to Van Soest and Wine (1967), 
and j_n vitro organic matter digestibility (IVOMD) by a 



47 



modification (Moore and Mott, 1974) of the Tilley and Terry 
(1963) procedure. Ash-free neutral detergent solubles 
(NDS) was calculated by substracting NDF from OM content of 
samples . 

Intake and apparent coefficients of digestibility 
were calculated for most of the feed quality components 
studi ed. 

Between-Trial Management of Animals 

Between trials, animals were handled and fed alike. 
The feeding regime consisted of standard all-forage diets, 
occasionally supplemented with soybean meal to meet N.R.C. 
(1968) nutritional requirements. On no occasion were 
these animals fed grain or concentrate feeds. Mineral 
supplements and water were always available. 

Statistical Analysis 

Statistical analyses of all data were carried out by 
least squares methods in fitting different regression models. 
Multiple comparison of means were made using Duncan's Range 
Test (1955). Duncan's Test was used only if least squares 
analysis of variance showed significant differences (P<.01, 
or P < .05). The SAS (Service, Barr and Goodnight, 1972) 
computer program library was utilized on an IBM 370-165 
computer at the Northeast Regional Data Center, University 
of Florida. 






48 



Results and Discussion 

Forage Composition 

The chemical composition and IVOMD of the forages 
are presented in table 3. Forage differed markedly in 
nutrient composition; ALF diet showed the highest CP (17.2%) 
and lowest NDF (48.3%) content, while LQB diet was lowest 
in CP (6.6%) and highest in NDF (78.7%) content. Diet HQB . 
showed intermediate values for CP (14.2%) and NDF (64.2%) 
content. The low standard deviation of these means indi- 
cated that little change occurred in the composition of the 
forage during the 18 months of the experimental period. In 
vitr o organic matter digestion (IVOMD) reflected differences 
in nutrient composition between LQB and the high quality 
forage diets (HQB and ALF), but did not reflect differences 
in composition between HQB and ALF diets (table 3). 

Live Weight Changes 

Live weights recorded at initiation of each trial 
are shown in figure 1. The animals averaged 34.5 kg at the 
beginning of trial I (10 months) and 54.6 kg at the begin- 
ning of trial IV (28 months). These values corresponded 

75 
to metabolic weights (W ) of 14.8 and 20.8 kg, respectively. 

No differences (P > .05) were detected between dietary 

treatments at any one age. The largest increase (P < .05) 






49 



TABLE 3. CHEMICAL COMPOSITION AND IN VITRO DIGESTION OF THE FORAGES. 
EXPERIMENT I 



FORAGE 1 



Criteria LQB HQB ALF 



2 
Percent of Dry Matter 



Organic Matter 95.5 ± .2 92.7 ± .2 88.7 ± .3 

Crude Protein 6.6 ± .2 14.2 ± .2 17.2 ± .2 

Neutral Detergent Fiber 3 78.7 ± .6 64.2 ± .6 48.3 ± .2 

Neutral Detergent Solubles 3 16.8 ± .5 28.5 ± .7 40.4 ± .3 

IVOND 4 , % 38.2 ± .2 61.0+1.4 61. 6 ±.3 



See table 2 for description of forages. 
2 

Mean + standard deviation of eight replications. 
3 

Ash-free. 

In vitro organic matter digestion, mean ± standard deviation of 12 
replications. 



50 



s 




o 




_j 






5 


ii 


(O 




-P 


CO 


10 


cr 


rO 


_j 


O 


- — - 


o 




Leo 

r CM 



3 

i 
i 

i 

O © Q 



CO CQ u_ 

_j re < 



.CM 

CM 



10 

sz . 
+J 

c 
c 

E 



U5 



O 



+-> rO 

c: rs 
cu o* 
E 

•I- -C 
1_ CD 
CU -i- 
Q.3C 
X 
UJ II 

C CQ 
•r- O" 

X 



i- 

+j 

o 

cu 

4- 

O 

£ 
O 

+j 



c 


«■-*. 


O 


- — . 


1 — 


ta 


>^ 


> 


+J 


»i — 


o 


+-> 


rO 


(O 


T3 


l/l 



CD t- 



c 


o 


o 


CD 


-a 


R3 


o 


(J 


c 


•1 — 


>i 


TJ 


c J 


CD 




>L 



T3 

CD 
"O 

s~ 

o 
o 
cu 

jL 
4-> 



(/I 

</> A3 

(O 4- 

i- r— 

cr> to 

« <4- 

■O r— 
3 fO 
p 

cu 

-Q U- 

tO 
+J ■ «1 

CO to 

to t/1 

O rO 

t_J S- 

>, to 

4-> "O 
•r- =3 

i — £ 

fO 5- 
23 CU 
0"-Q 



O 



o 

IT) 



O 



o 



o 



QJ 



cn 



5>! '1H9I3M AQOa 






51 

in live weight was observed between 10 and 16 months. 
Weights thereafter were not different. 

Nutrient Digestibility 

Trends in digestibility of 0M are shown in figure 2. 
As expected, the forage with the highest content of NDF 
(LQB) showed the lowest (P < .05) digestibility of 0M, where- 
as HQB and ALF were similar (P > .05) (Appendix table 21). 
In all forages, 0M digestibility was lowest at 10 months, 
increased with maturity to 22 months (P < .05) and then 
declined to a value similar to that observed at 10 months 
(Appendix tabl e 21 ) . 

Digestibility of NDF followed a pattern similar to 
that of OH (figure 3; Appendix table 21). In all diets, 
it was lowest at 10 months, increased (P < .05) to a maxi- 
mum at 22 months, and then decreased (P < .05) at 28 months 
to about 40 percent for LQB and 53 percent for HQB. Di- 
gestibility of NDF was intermediate in ALF and differed 
(P < .05) between ages. The largest change in NDF digest- 
'i'.n'lity of ALF, however, was the decrease (P < .05) between 
22 and 28 months. 

Voluntary Intake 

Relationship between intake and age 

Intake of 0M, in g/day, increased with age in all 
diets (figure 4) and differences (P < .05) between diets 



52 



60- 



>- 
i— 

5 50. 

CO 



UJ 
C3 



OS 



IE 

o 



CJ 
O 



40 



30 - 




.©" 



, ©-. 



-o 



©-*' 








LBQ 
HQB 
ALF 


o 




a 


1 

16 


AGE, months 


22 





Figure 2. 



10 



Digestibility of organic matter in Experiment I. 
(LQB = Low Quality Coastal bermudagrass ( Cynodon 
dactyl on ) : HQB = High Quality Coastal bermudagrass; 
ALF * alfalfa ( Medicag o sativa )). 



28 



53 



^s 



>- 

S— 



CD 



to 
o 



CfL 
UJ 

cc 



UJ 
CD 

cc 

LU 



QC 



LU 



.60-, 



50 . 



40 



30- 




B- 






o-.^. 



'ra 



•--© 



LQB o 

HQB © . 

ALF n ■ — 



10 



16 



AGE, months 



-r 

22 



28 



Figure 3. Digestibility of neutral detergent fiber in Experiment I, 
(LQB = Low Quality Coastal bennudagrass ( Cynodon 
dactyl on ); HQB = High Quality Coastal bermudagrass; 
ALF = alfalfa ( Medicago sativa )). 






54 






2500- 



ja-' 



T3 



UJ 



or: 



O 



o 
o 



2000 



J* 



1500 



1000 



s- 



._■-© 



_--o- 



O-" 



10 



16 



,-o.— ■ 



LQB o- 

HQB €>- 

ALF a. 

22 



28 



AGE, months 



Figure' 4. Voluntary intake of organic matter in Experiment I. 

(LQB = Low Quality Coastal bermudagrass (C ynodon dactyl on ); 
HQB = High Quality Coastal bermudagrass; ALF = alfalfa 
( Medicago sativa .) ) . . 






" 



55 



were accentuated as the animals matured (Appendix table 21). 
The increase in OM was also influenced by forage quality. 
In LQB the highest increase in OM intake (160 g/day, 
P < .05) was from 16 to 22 months. At 22 months OM intake 
values averaged 1400 grams per day. The same pattern of 
increase in OM intake (461 g/day, P < .05) was observed in 
the ALF fed animals between 16 and 22 months, but at higher 
intake levels (2400 g/day at 22 months). In the HQB diet, 
however, the largest increase in OM intake (344 g/day, 
P < .05) occurred earlier, between 10 and 16 months, when 
OM intake increased to approximately 1730 g/day at 16 months. 
A possible cause for these results will be discussed later. 

Intake of NDF followed a similar trend to that of 
OM intake (figure 5) although variations due to forage 
quality and animal age were observed. At 10 months, intake 
of NDF averaged 905, 951 and 851 grams per day for LQB, 
HQB, and ALF forage diets, respectively. As animals matured 
intake of NDF increased (P < .05) with all diets, but with 
LQB the rate of increase in NDF was more gradual. Overall, 
animals fed HQB consumed more (1250 g/day, P < .05) NDF than 
ALF fed animals (1160 g/day), which in turn showed higher 
(P < .05) NDF intake than animals fed LQB diet (1068 g/day). 

The intake of digestible OM (DOM) showed a linear 
increase in the first three trials, reached, a maximum at about 
22 months of age and then plateaued (figure 6; Appendix 
table 21). Intake of DOM was highest with ALF. Animals 



56 



1500- 



en 



< 



uj 

t— l 
I*. 



OS 



(2 



1300- 



1100- 



900' 



-I 



Ly_ 




10 



16 



22 



"T 

28 



AGE, months 



Figure 5. Voluntary intake of neutral detergent fiber in Experi- 
ment I. (LQB = Low Quality Coastal bermudagrass ( Cynodon 
dactylon); HQB - High Quality Coastal bermudagrass; ALF = 
alfalfa ( Medicago sativa ) ) . 









57 



to 
-a 

01 



UJ 

< 



1600 - 



a: 



P 



~ 1200 - 



/ ^ 



3 



O 

i — 

z 
< 
cs 

c 



cc 



UJ 

! 



800 ~ 



vr 



-e- 



.-■-&" 



400 - o- 



LQBo. 

HQB®- 

• ALFC- 



• -© 




AGE, months 

Figure 6. Intake of digestible organic matter in Experi- 
ment I. (LQB = Low Quality Caostal bermuda- 
grass ( C.ynodon dactyl on ); HQB = High Quality 
Coastal bermudagrass; ALF = alfalfa ( Medicago 
sativa )). 



58 



on LQB consumed approximately half the amount of DOM con- 
sumed by those on HQB and ALF. Intake of digestible NDF, 
on the other hand, was highest with HQB diet, but differ- 
ences between forage means, although statistically sig- 
nificant (P < .05), were not as large as those observed 
with DOM intake (table 4). 

The fact that the intake of digestible OM and di- 
gestible NDF did not show an increase in the last two 
trials while the intake of OM continued to increase indi- 
cates that either undigestible neutral detergent fiber 
and/or undigestible neutral detergent solubles may have 
progressively become a larger portion of the intake. Cal- 
culated data indicated (table 5) that both undigested 
(excreted) fractions tended to increase with increased OM 
intakes. Within a diet, as well as across diets, excretion 
of NDF (g/day) was highly correlated (P < .01) with NDF 
intake (g/day). For the ALF, HQB and LQB diets simple cor- 
relation coefficients (r) between excretion and intake of 
NDF were, respectively, .89, .92, and .94 (all values sig- 
nificant, P < .01). Excretion of NDS (g fecal NDS/day), on 
the other hand, was more highly correlated with intake of 
OM (g/day) (r = .92, P < .01) than with intake of NDF 
(g/day) (r = .57, P < .01) across forages. When fecal NDS 
is expressed as a percentage DM of the forage, it becomes 
an expression of metabolic fecal organic matter (MFOM), 
assuming that the true digestibility of forage NDS is 






59 



TABLE 4. INTAKE OF DIGESTIBLE NEUTRAL DETERGENT FIBER (NDF) AT 
DIFFERENT AGES OF THE ANIMAL. EXPERIMENT I 1 



Forage 




AGE, 


months 




Forage 
mean ± SD 


10 


16 


.22 


28 


LQB 


319 a 


42 1 b 


490 C 


489° 


430 X ± 92 


HQB 


468 a 


661 b 


767 C 


769 C 


666 Z ± 142 


ALF 


353 a 


487 b 


685 C 


607 d 


533 y ± 133 


Age mean 


380 


523 


647 


622 





Grams per day; each forage-age value represents the mean of eight 
observations. 
2 
See table 2 for description of forages. 

' ' Means in the same row bearing different superscripts are 
different (P < .05). 

x y z 
,J * Within a criterion, forage means bearing different super- 
scripts are different (P < .05). 



60 



TABLE 5. EXCRETION OF UNDIGESTED NEUTRAL DETERGENT FIBER AND NEUTRAL, DETER- 
GENT SOLUBLES AT DIFFERENT AGES OF THE ANIMAL. EXPERIMENT V. 



Criteria 



10 



AGE, months 



16 



22 



28 



. Forage 
mean ± SD 



Neutral Detergent Fiber 
Excretion (NDFX) 



LQB 2 


586 a 


595 a 


636 b 


736 C 


638 y ± 101 


HQB 


483 a 


560 b 


576 b 


71 3 C 


583 X ± 113 


ALF 


498 a 


572 b 


624 c 


813 d 


627 y ± 136 


Age mean 


522 


576 


612 


754 





Neutral Detergent Solubles 
Excretion (NDSX) 

LQB 95 a 11 7 b 148 C 146° 

HQB 124 a 178 b 211 C 259 C 

ALF 228 a 301 b 361° 435 C 

Age mean 149 198 240 280 



127 ± 28 
193 y ± 54 



33T 



85 



Grams per day; each forage-age value represents the mean of eight observa- 
tions. 

n 

See table 2 for decription of forages. 

a ' b ' C9 Means in the same row bearing different superscripts are different 
(P < .05). 

x ' y ' z Within a criterion, forage means bearing different superscripts are 
different (P < .05). 



61 



100 percent. Excretion of NDS differed (P < .05) between 
forages. Mean values for the LQB, HQB, and ALF diets were, 
respectively, 9.3, 9.7, and 13.7 percent of DM; with an 
overall average of 10.9 ± .22 percent. 



Relationship between intake and live weight 

Relative to body size, different expressions of in- 
take showed differences (P < .05) between ages for all forms 
of expression studied (table 6; Appendix table 22). Dif- 
ferences (P < .05) between forages also were evident for . 
all forms of expression of intake except for the intake of 
NDF. These results indicate that none of the forms of 
expression of intake, relative to live weight or metabolic 
size, was able to account for all of the differences in 
intake observed between ages (table 6). It also indicates 
that, regardless of forage quality, animals ingested simi- 
lar amounts (P > .05) of NDF per unit body weight and meta- 
bolic size, and the amount (g/day) consumed largely depended 
on animal size. As shown in table 6, intake of NDF whether 
expressed relative to live weight or metabolic size did not 
vary significantly (P > .05) between forages. Thus the 
dif f erences i n NDF intake between forages shown in figure 5 
were due primarily to differences in animal size measured 
at the end of each trial. Simple correlation analysis 
corroborated the relation between NDF intake and animal 
size. Across forages, NDF intake was the variable most 
highly correlated with live weight (r = .89) and with 



62 



TABLE 6. VOLUNTARY INTAKE OF ORGANIC MATTER AND NEUTRAL DETERGENT FIBER 
EXPRESSED AS FUNCTIONS OF BODY WEIGHT AND METABOLIC SIZE ACROSS 
AGES. EXPERIMENT il 



Criteria 




AGE, 


months 




Fo 

mean 


rage 


10 


16 


22 


28 


± SD 


Intake, g/W ■ /day 














Organic Matter (OM) 




LQB 2 


31. 6 b 


27. 8 a 


29. 3 a 


28. 9 a 


29. 4 X 


± 2.7 


HQB 


36. 8 b 


34. 4 a 


35.4 ab 


35.7 ab 


35. 6 y 


± 3.3 


ALF 


42. 7 b 


38. 5 a 


44. 3 b 


43. 8 b 


42. 3 Z 


± 4.2 


Neutral Detergent 
Fiber (NDF) 














LQB 


26. l b 


22. 9 a 


23. 8 a 


23. 9 a 


24. 2 X 


± 2.2 


HQB 


25. 2 a 


24. 3 a 


24. 2 a 


24. 6 a 


24. 6 X 


± 2.2 


ALF 


23. l b 


21. l a 


b 
24. 1 


23. 6 b 


23. X 


± 2.2 


75 
Intake, g/Wj^_ /day 














Organic Matter (OM) 




LQB 


76. 6 b 


71.6 a 


76. 8 b 


77. 4 b 


75. 6 X 


± 6.5 


HQB 


91. 3 a 


91. 7 a 


96.7 ab 


99. 5 b 


94. 8 y 


± 9.1 


ALF 


105. O a 


102. 5 a 


120. b 


122. b 


112. 4 2 


±12.5 


Neutral Detergent 
Fiber (NDF) 














LQB 


63. 4 b 


59. 2 a 


62.4 ab 


63. 9 b 


62. 2 X 


± 5.4 


HQB 


62. 5 a 


64.6 ab 


65.9 ab 


68. 5 b 


65. 4 X 


± 6.2 


ALF 


56. 9 a 


56. l a 


65. 6 b 


65. 8 b 


61. 1 X 


± 6.7 



Each forage-age value represents the mean of eight observations. 
2 
See table 2 for description of forages. 

' Means in the same row bearing different superscripts are different 
(P < .05). 

X V z 

'■" Within a criterion, forage means bearing different superscripts are 
different (P < .05). 



63 



metabolic size (r = .88) than any other form of intake ex- 
pression. Within a forage, however, DOM intake was as highly 
correlated (r = .85) as NDF intake with live weight. All 
the above correlation coefficients were highly significant 
(P < .01). A correlation matrix table containing the vari- 
ables studied is included in the Appendix (table 23). 

Expressing intake relative to body weight (W|* ) or 

7 5 
metabolic size (Wf ) reduced the coefficient of variation 

Kg 

for the different expressions of intake calculated across 
forage diets. This is illustrated in table 7 for digesti- 
ble organic matter intake. 

Repeatability of Voluntary Intake 

Repeatability (R) measures the correlation between 
repeated measurements of the same animal, and may be esti- 
mated by the ratio of the between-animal component to the 
total phenotypic variances (Falconer, 1972). In this study, 
the repeatabi 1 i ty of an animal's voluntary intake from one 
age to another was estimated from the corresponding intra- 
c 1 ass correl ati on , 

9 

°S 
(F) 

R ■ - 



2 2 
S (F) R 



o 
where cr. is the variance among sheep (S) within forage (F), 

o 5 (F) 
and c R is the within sheep variance. Standard error of 






64 



TABLE 7. VARIABILITY ASSOCIATED WITH DIGESTIBLE ORGANIC MATTER INTAKE 
EXPRESSED IN TERMS OF ABSOLUTE VALUES AND AS FUNCTION OF , 
BODY WEIGHT (Wj/ ) AND METABOLIC SIZE (W^ 75 ). EXPERIMENT I ! 



FORAGE 2 



Criteria LQB HQB ALF 



g/day 535 ± 107 1035 ± 199 1174 ± 260 

cv. (%) 3 (20.1) (19.2) (22.1) 

g/W 1,0 /day 12.0 ± 1.1 20.3 ± 1.9 23.3 ± 2.6 

cv. {%) (9.0) (9.5) (11.3) 

g/W* 75 /day 30.9 ± 3.1 54.2 ± 5.3 61.3 ± 7.8 

cv. {%) (10.2) (9.9) (12.7) 



Mean ± standard deviation of 32 observations, 
2 

See table 2 for description of forages. 
3 

Coefficient of variation. 






65 



repeatability estimates were calculated as proposed by 
Swiger et al . (1964). These values are presented in table 8 
Repeatability of forage intake ranged from .26 to .53, de- 
pending on the variable calculated. The highest and lowest 
value corresponded to NDF and DNDF when expressed in terms 
of g/W k ' • Variables expressing intake in grams per day 
showed as high R values as those expressing intake on live 
weight or metabolic size. When digestiblity was taken into 
consideration, however, R values were lower. In general, 
the highest R values obtained were for those expressions 

of intake relative to body weight (W ' ), followed closely 

7 5 
by those expressed in terms of metabolic size (W ). In 

all-comparison basis the repeatability scale was: DM > 

OM > NDF > DOM > DDM > DNDF. 

Rimm et al . (1957) working with Holstein and Guernsey 
heifers (16-26 months old) reported a repeatability of .32 
for roughage consumption when calculated at intervals of 
seven weeks. In twin cattle, Taylor and Young (1968) found 
that the average repeatability of an animal's voluntary 
intake ranged from age to age was .77, which is considered 
to be moderately high. 

It is difficult to make comparisons of repeatability 
values estimated under different experimental conditions 
and with other species of animals. In the case of Rimm _et_ 
al . (1957), the reported value appears to be considerably 
lower than that reported by Taylor and Young (1968) and the 
highest value obtained in the present study (R = .53). 






66 



TABLE 8.. ESTIMATES OF REPEATABILITY (R) OF INTAKE EXPRESSIONS, 

AND STANDARD ERROR (SE) OF REPEATABILITY. EXPERIMENT ll 



Expressions 



SE (R) 



9/day 

DM 

OM 

NDF 

DDM 

DOM 

DNDF 

g/W^/day 

DM 

OM 

NDF 

DDM 

DOM 

DNDF 

9/W" k /day 

DM 

OM 

NDF 

DDM 

DOM 

DNDF 



510 
.507 
,473 
.470 
.475 
.401 



523 
,522 
,529 
,339 
,410 
,262 



509 

,511 

511 

253 

,409 

,278 



104 

104 

107 

.107 

,107 

.111 



103 
103 
100 
112 
112 
111 



.104 
.104 
.104 
.111 
.111 
.111 



1, 



96 observations. 

"Letter(s) abbreviation are the the following: DM = dry matter; 
OM = organic matter; NDF = neutral detergent fiber; D prefix = 
digestible. 









67 



R 1 " rnm et al . ' (1957) based their R values on three 
measurements at intervals of seven weeks, while Taylor and 
Young (1968) based theirs over a period of several years. 
In our experiment, R values were based on four measurements 
taken at six months intervals. Thus, to designate an R 
value as being high or low without some objective standard 
would be arbitrary. Turner and Young (1969) suggested a 
way to set such standards by comparing the gain by selec- 
tion, as percent relative efficiency of selection (Q), 
when a single record is compared to k number of records. 

The above criterion was applied to the R values ob- 
tained in this study and compared to the value reported by 
Rimm et al ■ (1957). The following equation (Turner and 
Young , 1 969 ) was used : 



Q - 100 / 1 + jlfc -T) R 



when k = 2 is used as a standard, the authors define: 

a) high repeatability as a value of R which gives 
Q > 90. 

b) medium when 80 _< Q <_ 90, and 

c) low repeatability when £ 80 percent, when k = 1. 
Applying this scale an R value of .32 when k = 2, 

would give a Q value of 81.5 percent, and corresponds to a 
medium value of repeatability. A value of .53 with k = 2 
would result in Q = 87.5 percent and would fall in the 
upper medium level of repeatability. 






63 



Repeatability for other characteristics in sheep has 
been summarized by Turner and Young (1969). 

Regression Analysis of Forage Intake on Body Weight 

Because similar results were obtained when intake 
was based on live weight as when metabolic size was used 
(table 7), a regression analysis was carried out to deter- 
mine what power of body weight "best" fit the data. Within 
each forage diet, the common logarithm of a variable express- 
ing intake was regressed on the common logarithm of body 
weight (BVJ. ). For DOM intake (DOMI), the regression model 
utilized was the following: 

L0G 1Q DOMI = 3 + 3-,Uog 10 Bk' kg ) + e (1) 

The statistics of fit for this analysis are shown in table 9 
The regression lines showed similar slopes for LQB and HQB, 
but different intercepts. There is no indication of non- 
linearity. The regression coefficients for body weight 

were very close to one, and body weight accounted for a 

2 
significant (P < .01) fraction (R = .77-. 80) of the varia- 
tion in the logarithm of DOMI. 

The above model (1) was fitted to the intake data 
from each forage-age combination, and the resulting regres- 
sion lines were compared, within forages, with those from 
a pooled within ages model (Snedecor and Cochran, 1967): 






69 



TABLE 9. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR THE 
LOGARITHMIC REGRESSION OF DIGESTIBLE ORGANIC MATTER 
INTAKE (Y) ON BODY WEIGHT (X). EXPERIMENT I 1 





Forage 


n 


b O 


b l * Sb l 


S 

y.x 


R 2 


P > F 


LQB 


32 


1.028 


1.030 ± .093 


.040 


.80 


.0001 


HQB 


32 


1.478 


.899 ± .090 


.042 


.77 


.0001 


ALF 


32 


1.232 


1.077 ± .099 


.048 


.80 


.0001 



1 S 

Log-,Q Y = b~ + b, (Log, X); b-, = standard error of regression 

coefficient, y.x = standard error of estimate, R~ = coefficient of 
determination. 
2 
See table 2 for description of forages. 






70 



L0G 1Q DOMI = 3 + 6-j (LOG 1Q BW kg ) + 3 2 AGE + e (2) 

Within forage diets models (1) and (2) did not differ 
in residual variances; and only ALF differed (P < .01) in 
slope and elevation (P < .01); thus indicating significant 
variation from age to age in the DOMI of ALF relative to 
body weight. This, however, is likely to be due in part to 
significant (P < .05) variations observed in the M digesti- 
bility across ages in that particular diet because, when 
DOMI was substituted by OMI as the independent variable 
in the above regression model previous differences (P < .01) 
in slope of the ALF diet were reduced to a lower level of 
significance (P < .05). 

Test for differences in slope of regression lines 
among forages also was performed by comparing the pooled 
within ages model (2) with a pooled within forage age model : 
L0G 1Q DOMI = B Q + ^(LOG-jq BW fe ) + 3 2 FORAGE + 63 AGE 

+ e (3) 

The test showed no significant difference (P > .05) 
in slope of regression lines among forage diets. 

Regression analysis fitting the above mentioned 
models was also carried out for DMI , OMI and NDFI (Appendix 
tables 24, 25 and 26). 






71 



Removal of Body Size Effect on Intake 

If intake is to be used as an index of forage quality, 

the effect of animal size on the measured intake must be 

effectively removed. To study this aspect, the relationship 

of DOM intake (DOMI) per kilogram metabolic size raised to 

the .75 power (Wr,„ ), and per kilogram body weight (W." ), 

Kg K g 

on body weight (BW) in kilograms was determined by regres- 
sion analysis fitting the following models: 

DOMI/W'g 5 = B + B 1 (BW kg ) + e; and 

■ DOMI/Wj- = 3 Q + Bl (BW kg ) + e 

When intake was expressed as grams of DOM consumed 
per kilogram of metabolic size, as shown in figure 7, and 
table 10, the relationship was linear with positive slopes. 
With this model body weight accounted for 8 to 23 percent 
of the variation in intake (table 10). However, when in- 
take was expressed as grams consumed per kilogram of body 
weight (figure 8), the relationship between intake and 
body weight was minimized and body weight accounted for 
not more than four percent of the variation in intake 
(table 10). Other expressions of intake were also studied, 



but they did not appear to improve the results obtained 

with DOMI/W, " as an indepe 
Kg 

(Appendix table 27 and 28). 



with DOMI/W. " as an independent variable in the model 
K 9 






72 









| 



OS 

o 
—I 

CO 



LU 
CD 




20 1 



LQB -o 

HQB ® 

ALF jd 



— j— - 

20 



40 



60 



80 



BODY WEIGHT, kg 



Figure 7. Linear regression of digestible organic matter intake 
per kg of metabolic size on body weight. Experiment I. 
(LQB - Low Quality Coastal bermudagrass (Cynodon 
dactyl on) ; HQB - High Quality Coastal bermudagrass; 
ALF = alfalfa (Medicago sativa ) ). 



73 



TABLE 10. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR THE LINEAR 
REGRESSION OF TWO EXPRESSIONS OF DIGESTIBLE ORGANIC MATTER 
INTAKE. EXPERIMENT il 



Variable 


(Y) 


n 


b 


b l* 


S h 
b l 


S 

y.x 


R 2 


P > F 


DOMI/W* 75 


















LQB 2 




32 


22.609 


.187 ± 


.063 


2.8 


.22 


.006 


HQB 




32 


45.610 


.167 ± 


.099 


5.2 


.08 


.103 


ALF 




32 


41.610 


.402 ± 


.134 


7.1 


.23 


.005 


DOMI/W 1 ' 


















LQB 




32 


11.720 


.006 ± 


.020 


1.1 


.00 


.790 


HQB 




32 


22.400 


-.040 ± 


.030 


1.9 


.03 


.280 


ALF 




32 


21.620 


.033 ± 


.050 


2.6 


.01 


.52 



1 C 

Y = b Q + b-jX; b-j = standard error of regression coefficient; y.x = 

standard error of estimate; R 2 ■ coefficient of determination. 
See table 2 for description of forages. 



74 



o 

I— -M 

3 



< 



DS 



30- 



20- 



CD 

g 10 

UJ 

_I 

CO 



LU 

CD 
►—* 

Q 




.jn 



— ©- 




T 

20 



40 60 
BODY WEIGHT, kg 



Figure 8. Linear regression of digestible organic matter intake 
per kg of body weight on body weight. Experiment I. 
(LQB = Low Quality Coastal bermudagrass ( Cynodon 
dactylon ): HQB = High Quality Coastal bermudagrass; 
ALF = alfalfa (Medicago sativa)). 



75 



Heaney (1970) indicated that for his forages 
(timothys, alfalfa, and grass-legumes mixtures) and animals 
in different physiological states (ewes, rams, wethers), 
less variation was obtained by expressing intake in terms 
of metabolic size, in which case body weight accounted 
for less than 10 percent of the variation. No specific 
variable of intake was mentioned but presumably Heaney 
was implying dry matter intake. 

In the present study the experimental animals were 
wethers and, therefore, this must betaken into cons iderati on 
when comparing these results with those observed by 
Heaney (1970). 






EXPERIMENT II 

EFFECT OF ANIMAL AGE, SIZE, AND FATNESS 
ON VOLUNTARY INTAKE OF PELLETED FORAGES 



In the previous experiment, animal age, weight and 
voluntary intake were studied and the changes in live weight 
and intake associated with the advancement of age reported. 
Age and weight were confounded and, as a consequence, clean 
estimates of each effect on intake were not obtained. Stated 
in other terms: was the increase in absolute values of in- 
take during the experiment due to a concomitant increase in 
body weight alone, or was it also due to age? Further, what 
effect does animal age have on forage intake? In an attempt 
to clarify these i nterrogants , the present experiment was 
conducted. 

Procedure 

Experimental Design 

In this experiment a group of thirty six Suffolk x 
Native crossbred wethers, representing three ages and dif- 
ferent sizes within each age, were randomly alloted to two 
Coastal bermudagrass pelleted hay diets (table 11). The 
diets were offered ad .li bitum and the intake and digestibility 

76 






77 



TABLE 11. FACTORIAL ARRANGEMENT OF TREATMENTS 
EXPERIMENT II 




LQB2 - Low Quality Coastal bermudagrass (Cynodon 
dactyjoii), experiment II; HQB2 ■ High QuaTit7~~ 
Coastal bermudagrass, experiment II. 

Number of animals in each Forage-Age treatment 
combination. 



78 



of diet components measured in a single trial using the same 
procedure as in experiment I. 

Live Animal Weighing 

At the termination of the intake and digestion trial, 
the animals were weighed and, according to the previous di- 
etary treatments, assigned to two group-pens where they re- 
mained for a 72-hour pre slaughter period. During the first 
48 hours of that period the animals were allowed free access 
to their corresponding diet. Feed but not water was then 
withdrawn for the remaining 24 hours. During the preslaughter 
period, three additional live weight measurements were re- 
corded at intervals of 24 hours, giving a total of three 
full body weight measurements and one measurement, the last 
weight recorded after 24-hour without food, of shrunk body 
weight. 

Carcass Measurements 



Prior to slaughtering, the animals were sheared and 
the weight of the entire wool recorded. Slaughtering was 
carried out at the Meats Laboratory abattoir following stand- 
ard procedures. Carcass weights were recorded to the near- 
est .25 pounds. Weights of the full and empty digestive 
tracts were also recorded. 

After a 48-hour chill at 3°C, the carcasses were 
graded and evaluated as suggested by Kemp (1952): rib-eye 



79 



area (in ) and fat thickness (mm) over rib-eye were measured 
at the 12th rib by separation of the rib and loin between 
the 12th and 13th thoracic vertebrae; kidneys plus kidney 
fat were removed from the chilled carcass, weighed and ex- 
pressed as percent of the carcass; and the untrimmed leg was 
obtained by cutting perpendicular to the line of back leav- 
ing one lumbar vertebra attac'hed, weighed and expressed as 
percent of carcass weight. Carcass fat and lean content 
were estimated from a multiple regression equation (Latham 
et aj_. , 1966) by fitting the above measured parameters into 
the following prediction equation: 

FAT {%) = 68.73 - 4.28(in rib-eye area) + .68(mm fat thickness 
over eye) + .58(% kidney + kidney fat) - 1.19(%leg) 

LEAN(%) = 25.08 + 3.33(in 2 rib-eye area) - .41 (mm fat thickness 
over eye) - .66(55 kidney + kidney fat) + .93(% leg). 

Statistical Analysis 

All data was subjected to statistical analyses as 
described in experiment I. 

Results and Discussion 
Forage Composition 



The chemical composition of the two pelleted Coastal 
bermudagrass forages offered in this experiment is presented 



80 



in table 12. These forages were very similar in composition 
to the bermudagrasses used in experiment I. Crude protein 
ranged from 7.2 to 14.8 percent, and the NDF fraction from 
78.2 to 61.7 percent, for the low quality (LQB2) and high 
quality (HQB2) Coastal bermudagrass pellets, respectively. 

Animal Age and Digestibility 

The digestibility coefficients in each Forage-Age 
combination are presented in table 13. No differences 
(P > .05) were observed in the digestibilities due to age 
(Appendix table 33). There were, however, differences 
(P < .01) in digestibility due to dietary forages in all 
variables studied (Appendix table 33). Within diets stand- 
ard deviations were not higher than 3.5 percent digestibil- 
ity units in the variables studied (table 13). These results 
indicate that digestibility of forages was little affected 
by animal age or size, but depended primarily on forage 
q u a 1 i ty . 

A..ima1 Age, Body Size and Voluntary Intake 

The trend in absolute values of DOM intake (grams per 
day) at each Age-Diet treatment combination is illustrated 
in figure 9. No difference (P > .05) was observed in the 
intake of HQB2 or LQB2 DOM between the 12 and the 24 month 
old sheep. The 36 month old group, however, consumed 






81 



TABLE 12. CHEMICAL COMPOSITION AND IN VITRO DIGESTION OF THE FORAGES 
FED IN EXPERIMENT II 



FORAGE 1 



Criteria LQB2 HQB2 



Percent of Dry Matter 

Organic Matter (OM) 

Crude Protein (CP) 

Neutral Detergent Fiber (NDF) 

Neutral Detergent Solubles 2 (NDS) 

IVOMD 3 , % 



See table 11 for description of forages 
2 

Ash-free. 
3 

In vitro organic matter digestion. 



96.4 


93.3 


7.2 


14.3 


78.2 


61.7 


18.2 


31.6 


33.5 


63.5 



82 



TABLE 13. EFFECT OF AGE AND FORAGE QUALITY ON NUTRIENT DIGESTIBILITY. 
EXPERIMENT II 1 







AGE, 


months 




Forage 
mean ± SD 


Criteria 


12 


24 


36 


Organic Matter (OM) 










LQB2 2 


33.3 


35.3 


34.0 


34. 2 a ± 2.9 


HQB2 


56.6 


55.4 


55.6 


55. 9 b ± 1.4 


Age mean 


45.0 


45.4 


44.8 




Neutral Detergent 
Fiber (NDF) 










LQB2 


31.3 


33.6 


31.7 


32. 2 a ± 3.5 


HQB2 


53.1 


51.0 


51.9 


52. l b ± 2.3 


Age mean 


42.2 


42.3 


41.8 





Percent; each forage-age value represents the mean of six observations. 
2 
See table 11 for description of forages. 

Within a criterion, forage means bearing different superscripts are 
different (P < .05). 



■ 



83 



1350- 



§ 1100 

en 









o 



s 

o 



CO 
I — I 

(- 

CO 
LU 

CD 

Q 



800- 



550" 



300 



.^.-o 



© 



©-•' 



LQB2 <>-• 
HQB2 ©_ 



12 24 

AGE, months 



36 



Figure 9. 



Intake of digestible organic matter at each forage-age 
combination. Experiment II. (LQ.B2 ■ Low Quality 
Coastal bermudagrass ( Cynodon dactyl on ), Experiment II; 
HQB2 - High Quality Coastal bermudagrass, Experiment II) 



' 



84 



approximately 275 grams more (P < .05) of the HQB2 than did 
the younger groups. With LQB2 no significant differences 
(P > .05) were observed between age groups. 

Expressing intake values relative to body weight 
(DOM intake/W ' ), as shown in figure 10, completely removed 
the effect of age (P > .05) on the intake of HQB2 as well 
as LQB2. Daily intake of DOM' averaged 8.4 + 1.2 and 20.7 ± 
1.5 g/wV°, for the LQB2 and HQB2 diets, respectively. Val- 
ues for the other variables studied are presented in Appen- 
dix table 29. 

Across diets, intake of NDF was the variable most 
highly correlated with body weight (r = .78, P < .01). 



Statistical Variation Associated with Different Expressions 
of Intake Relative to Body Size 

In order to determine the "best" expression of intake, 
relative to animal size, several forms of expressing body 
size were studied. Animal size was then expressed as full 
(FBW), 24-hour shrunk (Sh'BW), empty (EBW), and fat-free 
empty (FFEBW). Empty body weight was estimated by adjusting 
for contents of digestive tract in shrunk weight, and FFEBW 

by adjusting for body fat estimated in empty body weight. 

7 5 
Metabolic size (FBW ) and hot carcass weight (H0TCW) were 

also considered. 

Simple statistics of these measurements appear in 
table 14. Coefficients of variation- were lowest for metabolic 






85 



25 



>> 

-a 



o 

r— -V 



15" 



— © 



o 
a 



o— 



i 0- 



© 

LQB2o 

HQB2® 



12 



— — s — ' — *" 

24 . 

AGE, months 



36 



Figure 10. 



Intake of digestible organic matter per kg body 
weight at each forage-age combination. Experi- 
ment II. (LQB2 = Low Quality Coastal bermuda- 
grass ( Cynodon dactyl on ); HQB2 = High Quality 
Coastal bermudagrass). 



86 



TABLE 14. SIMPLE STATISTICS OF DIFFERENT FORMS OF EXPRESSION 
OF BODY SIZE. EXPERIMENT II 



' 




KILOGRAMS 1 




Variable 


X ± SD 


CV.(%) 2 


Full Body (FBW) 


49.4 ± 9.6 


19.5 


Shrunk Body (SHBW) 


46.5 ± 9.1 


19.5 


Empty Body (EBW) 


38.9 ± 8.3 


21.2 


Hot Carcass (HOTCW) 


23.2 ± 5.4 


23.3 


Fat Free Empty (FFEBW) 


31.8 ± 6.0 


19.0 


Metabolic (FBW 75 ) 


18.6 ± 2.7 


14.8 



Mean ± standard deviation of 36 observations. 
2 
Coefficient of variation. 






87 



size (14.8%) and highest for hot carcass weight (23.3%), 
while the rest were approximately 20 percent. Within forage 
coefficients of variation for these variables were lower, 
but proportionally similar. 

Intake values were calculated on the basis of each 
expression of body size, to detect any improvement in reduc- 
ing the variability among anfmals. Partial results are pre- 
sented in table 15. The coefficients of variation might ap- 
pear surprisingly high, but this may be explained by the 
range in variation in the experiment itself associated with 
forage quality, animal age, and body weights. However, one 
varable, NDFI, stands out for its low coefficient of varia- 
tion (16 - 18%) as compared to other variables. When ex- 
pressed in terms of FBW or EBW, NDF intake showed the low- 
est variation. This may be advantageous when intake com- 
parisons are made among pelleted forages differing widely 
in quality. 

Among the body size variables studied, EBW appears 
to have an overall slight advantage over the other variables 
because of smaller variation for expressing intake. This 
variable, EBW, showed a high positive correlation with FBW 
(r = .97) and with SHBW (r - .99) (Appendix table 30) and 
therefore, may be accurately estimated from full body weight 
by linear regression analysis. The regression equations for 
estimating EBW (Y) from (1) FBW (X) and from (2) SHBW (X) 
were : 






88 



TABLE 15. SIMPLE STATISTICS ASSOCIATED WITH EXPRESSIONS OF VOLUNTARY INTAKE 
RELATIVE TO BODY SIZE. EXPERIMENT II 



Intake per Kilogram Body Size per Day 



1 



Organic Matter 



Total 



Digestible 



Neutral Detergent Fiber 
Total Digestible 



Full Body 



30.8 ± 7.2 
(23.4) 



Shrunk Body 32.8 ± 7.9 

(24.2) 



Empty Body 



Hot Carcass 



Metabolic 



39.2 ± 8.5 
(21.6) 

66.2 ± 15.2 
(23.0) 

81.6 ± 20.3 
(24.9) 



Fat Free Empty 47.9 ± 10.9 

(22.7) 



14.5 ± 6.4 
(44.0) 

15.5 ± 6.9 
(44.4) 

18.3 ± 7.6 
(41.4) 

30.9 ± 12.9 
(41.9) 

38.6 ± 17.6 
(45.5) 

22.5 ± 9.6 
(42.9) 



22.3 ± 3.5 
(15.8) 

23.8 ± 4.1 
(17.1) 

28.5 ± 4.5 
(15.9) 

48.1 ± 8.8 
(18.2) 

58.9 ± 9.8 
(16.7) 

34.7 ± 5.6 
(16.1) 



9.6 ± 3.4 
(35.2) 

10.2 ± 3.7 
(35.9) 

12.1 ± 3.9 
(32.7) 

20.5 ± 6.9 
(33.6) 

25.4 ± 9.3 
(36.6) 

14.8 ± 5.1 
(34.2) 



1 



Mean ± standard deviation (with coefficient of variation in parenthesis) 
of 36 observations. 






89 

(1) Y = -2.298 + .834X; and 

(2) Y - -2.429 + .889X. 

Both of these models accounted for 95 percent of the 

2 
variation (R = .95). The regression coefficient (b,) from 

model (1) agrees with that reported by Ellenberger et al . 

(1950) with cattle (b ] = .817 FBW). 

The statistics of fit for models (1) and (2) and for 

other regression models associated with carcass weight are 

presented in table 16. 

Interrelationships Among Animal Age, Body Height, Degree of 
Fatness and Voluntary Intake ~ 

Several researchers (Bines et al . , 1969; Ferguson, 
1956; Foot, 1972; Tayler, 1959) have indicated that increas- 
ing degree of fatness of an animal may have a depressing ef- 
fect on feed intake; and present evidence indicates that body 
weight and age are generally correlated. Yet, there appears 
to be no attempt made to partition the variance components 
that are attributed to the variation in intake. 

In the present experiment one of the parameters 
studied was fat content of the carcasses, which was esti- 
mated from multiple regression equations (Procedure, exper- 
iment II). The results are shown in a bar graph (figure 11) 
where each column denotes a Diet-Age combination and re- 
presents the weight of the chilled carcass; the transverse 






90 



TABLE 16. LINEAR REGRESSION EQUATIONS AND STATISTICS OF FIT FOR RELA- 
TIONSHIPS AMONG VARIOUS BODY MEASUREMENTS. EXPERIMENT II T 



Varia 


bles 2 


b 


b l 


± 


b l 


S 

y.x 


R 2 




Y 


X 


P > F 


EBW 


FBW 


-2.298 


.834 


+ 


.033 


1.93 


.95 


.0001 


EBW 


SHBW 


-2.429 


.889 


+ 


.033 


1.79 


.95 


.0001 


HOTCW 


EBW 


-2.115 


.651 


+ 


.011 


.58 


.99 


.0001 


CHCW 


EBW 


-2.104 


.639 


+ 


;on 


.58 


.99 


.0001 


CHCW 


HOTCW 


-.028 


.981 


+ 


.004 


.14 


.99 


.0001 


DGTW 


SHBW 


-.698 


.115 


+ 


.007 


.41 


.87 


.0001 


DGTW 


EBW 


-.403 


.130 


+ 


.006 


.32 


.92 


.0001 



1 s s 

Y = b Q + b-jX; b, = standard error of regression coefficient, y.x = 

standard error of estimate, R = coefficient of determination. 
2 
EBW, FBW, and SHBW = empty, full and shrunk body weights, respectively; 

HOTCW and CHCW = hot and chilled carcass weight, respectively; and 

DGTW = empty digestive tract weight; all in kilograms. 



91 



50 



or 
o 



Figure 11 




CHILLED CARCASS WEIGH: 



CARCASS FAT 



L = LQB2 
H - HQB2 



30 




L H 

AGE, 12 mo. 



L H 
AGE, 24 mo. 



L H 
AGE, 36 mo. 



Effect of animal size and forage quality on carcass 
fat content. Experiment II. (LQB2 = Low Quality 
Coastal bermudagrass ( Cynodon dac tyl on ) ; HQB2 = 
High Quality Coastal bermudagrass). 



* 






92 



lined portion denotes the amount (kg) of fat, also calculated 
as percent of the chilled carcass weight. In general the 
amount of fat in the carcasses reflected the quality of the 
forage diet. Carcasses from the high quality diet contained 
similar amounts of fat (32 - 35%) based on chilled carcass 
weight. However, the fat content of the 36 month old car- 
casses from the low quality d'iet was considerably larger and 
differed significantly (P < .05) from the other two age 
groups (Appendix table 31). 

In view of these results, a multiple logarithmic re- 
gression analysis on digestible organic matter intake (DOMI) 
was performed for each diet, fitting the data to the follow- 
ing model : 



L-DOMI ■ 6 Q + 3-j (L-FAT) + B 2 (L-FBW) + B 3 (AGE) + e , 

where L-DOMI stands for L0G 1Q of DOMI, L-FAT for L0G 10 of 
grams of fat in the chilled carcass weight of the animal, 
L-FBW for L0G 10 kilograms of full body weight, and AGE for 
the age of animal in months. The results of this analysis 
and statistics of fit are presented in table 17. In the low 
quality diet (LQB2), the regression coefficients for the in- 
dependent variables FEW and FAT proved significant (P < .01); 
whereas in the high quality diet (HQB2) only the beta value 
of the FBW regression coefficient was significant. In both 
diets, though, FAT showed a negative effect on the intake of 
digestible organic matter. 



9 



o 



TABLE 17. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR THE MULTIPLE 
LOGARITHMIC REGRESSION OF DIGESTIBLE ORGANIC MATTER INTAKE (Y), 
ON FULL BODY WEIGHT, CARCASS FAT AND ANIMAL AGE. EXPERIMENT II 1 



S 2 
y.x R P > F 



Forage Y 


X's 






b. ± S b. 




LQB2 

L-DOMI 3 














Intercept 


b O 


s 


2.226** ± 


.221 




L-FAT 


b l 


s 


-.543** ± 


.123 




L-FBW 


b 2 


= 


1.441** ± 


.239 




AGE 


Db 3 


= 


-.039 ± 


.011 






Db 4 


s 


.033 ± 


.010 






Db 5 


s 


.006 ± 


.001 



029 .88 .0001 



HQB2 

L-DOMI 



Intercept b Q = 2.042** ± .463 .036 .85 .0001 



L-FAT 


b l = 


-.347 


± .253 


L-FBW 


b 2 = 


1.367** 


± .385 


AGE 


Db 3 = 


-.007 


± .013 




Db 4 - 


.003 


± .014 




Db 5 = 


.004 


± .001 



on 



1 Log 10 Y = b Q + b-^Log^ FAT) + b 2 (Log ]0 FBW) + b 3 AGE ; b. - regressi 

S S 

coefficient, b. = standard error of regression coefficient, y.x = 

1 ? 

standard error of estimate, R~ = coefficient of determination, Db = dummy 

variable for AGES 12 (Db 3 ), 24 (Db 4 ), 36 (Dbg). 

See table 11 for description of forages. 

Common logarithm (L-) of dependent and independent variables: DOMI = 

digestible organic matter intake, grams/day; FBW = full body weight, kg; 

FAT = grams of fat in chilled carcass; AGE = age of animal, months. 
** 

P > T = .01. 



GENERAL DISCUSSION 
Digesti bi 1 i ty 

Digestibility of the diet, as results from experi- 
ment II demonstrated, was not shown to depend on animal age 
or weight, but mainly on feed quality. These results are 
in agreement with those of Hadjipieris et al . ■ (1965) and 
Graham and Searle (1972) who found rather small differences 
in digestibility between animals of diverse age and size; 
they are, however, in disagreement with the results from 
experiment I, where changes in digestibility were observed 
when determined at different times (physiological ages) in 
the animal . 

Since a set of experimental conditions (temperature, 
humidity, level of feed intake) were confounded with physio- 
logical changes in the animal, it is not possible to signify 
the factor(s) responsible for the changes in digestibility. 
It does indicate, however, that the correlation (intra- 
class) of animal's feed digestibility coefficient is low 
(R = .08, for OMD) when measured successively at intervals 
of six months under ad l ibitum feeding conditions. This 
should not imply, however, that under present conditions 
mean digestibility coefficients have a low predictive value. 



94 



95 



Within a forage, mean digestibility coefficients showed 
small variability (c.v. < 7% for OMD) among animals and 
across ages, which was expectedly higher than the within 
forage-age variation (range 2.0-5.0% c.v.j. 

Digestibility of the NDF fraction in the high 
quality Bermudagrasses (HQB and HQB2) were very similar 
in experiments I and II (53 and 52% respectively), this 
was not the case, however, i n the low quality Bermudas. Mean 
NDF digestibility of the LQB and LQB2 diets in experiment I 
and II were approximately 40 and 32 percent, respectively. 
The difference (8%) in digestibility is not explained by 
chemical composition, which showed very similar NDF content, 
Laredo and Minson (1975) have indicated that grinding and 
pelleting will not alter the chemical composition of the 
fiber or the protective action of the lignin. Thus, it 
appears that the difference in digestibility of the low 
quality Bermudas (LQB and LQB2) may have been due to dif- 
ferences in the physical organization of molecules within 
plant cell walls (Bailey and Jones, 1971; Van Soest, 1959). 

In vitro organic matter digestibility (IVOMD) is a 
common laboratory procedure for predicting in vivo digest- 
ibility values, and has been successfully utilized as a 
routine screening procedure for forage quality evaluation 
in plant breeding programs (Moore and Mott, 1973). In the 
present study IVOMD values were very much in agreement with 
i n vivo values in the low quality diets (LQB and LQB2) of 






96 



experiments I and II, but overestimated j_n vivo OMD values 
in the high quality diets (HQB and HQB2) and the alfalfa 
diet of experiment I. Grinding and pelleting is known to 
depress OMD (Minson, 1963), which along with high intake 
levels may have been the cause for lower J_n vivo digestibil- 
ity values. Nonetheless, simple linear regression analysis 
of 14 forage means, 12 from experiment I and two from experi- 
ment II, showed a high correlation coefficient (r = .95) be- 
tween IVOMD and in vivo observed values. The resulting re- 
gression equation was: 

OMD % = 14.030 + .685 IVOMD 

( S y.x . = 2.86 ; R 2 - .90) 

There are only 14 points on this curve representing 
five pelleted forages, four of which are Coastal Bermudagrass 
and one Alfalfa. Therefore its usefulness as a prediction 
equation is limited. 

Feed digestibility may be accurately predicted by de- 
termining the relationship between percent digestible organic 
matter (DOM) and percent digestible neutral detergent fiber 
plus neutral detergent solubles (DNDF + NDS), corrected for 
undigestible neutral detergent solubles (UNDS) or metabolic 
fecal organic matter (Barnes, 1973; Moore and Mott, 1973; 
Velasquez, 1974). Data from Florida (Moore, Golding and 
Barnes, 1975) on 43 grass and 9 legume hays indicate that a 
value of 10 percent for UNDS is applicable for most hays when 






97 



calculating digestible energy values, The following Summa- 
tive Equation was then applied to the present data in a 
linear regression analysis: 

DOM = DNDF + NDS - 10 

The resulting regression equation, 

Y = 3.990 + .896 X ± .01 , 

accounted for 95 percent of the variation attributed to DOM, 
and showed a low standard error of estimate (± 1.76). Resid- 
ual (Y - Y) values obtained from fitting the prediction equa- 
tion to 132 individual observations did not deviate more 
than 4.5 percent digestibility units in a relatively wide 
range (29 - 57%) of DOM values. 

It is considered, therefore, that a value of 10 per- 
cent for metabolic fecal organic matter or UNDS may also be 
used with pelleted forage diets. Actually UNDS values for 
these data differed slightly from the above value, and varied 
with forage quality, but was not affected by age of animal. 
Overall mean and standard deviation (S.D.) of UNDS values 
were 10.9 ± 2.2 and 10.8 ± 0.7, for experiments I and II, 
respecti vely . 

Because in both present experiments UNDS (g/day) was 
highly correlated with DMI (g/day) and 0MI (g/day) 5 the ef- 
fect of these and other variables on UNDS was studied on all 
data (132 animal observations) by stepwise regression analysis 






98 



(table 18). The most influential variable was DMI , or OMI in 
alternate model II, accounting for a significant portion 
(86 - 89%) of the variation in UNDS. Addition of forage OM 
{% of DM) content and NDF excretion further reduced the vari- 
ation. 

As percent of DMI, all-data mean UNDS value was 11.3 
percent, which proved lower than the 12.9 value used by Van 
Soest (1967) and higher than the one (9.5%) reported by 
Minson (1971) for Panicum . When UNDS was calculated as per- 
cent of OMI the value obtained was 12.2 percent, very close 
to the value (12%) reported by Terry, Cammell and Osbourn 
(1972). ' 

Statistics of fit and regression coefficients for the 
"best" four variables predicting model for UNDS (g/day) are 
given in table 19. 

Voluntary Intake 

The nutrient composition and intake values in the high 
quality Bermuda grass diets of experiments I and II were very 
similar. Voluntary consumption of DOM was 20 and 21 grams/ 

w k ' g /day in experiments I and II, respectively, and 24.6 and 

1 
25 g/W " /day for NDF, respectively. Since nutrient compo- 
sition of the low quality forages were very similar in both 
experiments also, one would have expected similar intakes 
too. However, average consumption of DOM was about 30 percent 



99 



TABLE 18. SUMMARY OF STEPWISE REGRESSION OF DIFFERENT VARIABLES ON 
[INDIGESTIBLE NEUTRAL DETERGENT SOLUBLES (UNDS) 



Multiple In , ra3fo Dafi „^ nn F value 



to enter 



Step Variable - Increase Reduction 

1 2 2 

Number entered R R . in R in MSE or remove 



Model I 



1 


DMI 


.946 


.895 


.895 


1019.68 


1104.98** 


2 


OM 


.960 


.922 


.027 


258.58 


45.18** 


3 


NDFX 


.966 


.934 


.012 


115.51 


24.08** 


4 


NDS 


.967 


.936 


.002 


9.63 


2.94 


5 


w 1 - 


.967 


.936 


.000 


3.60 


.28 







Model II 


.927 


.860 


.860 


.956 


.914 


.054 


.964 


.930 


.016 


.965 


.932 


.002 


.965 


.932 


.000 



1 DMI .927 .860 .860 1354.35 

2 OM .956 .914 .054 514.26 

3 NDFX .964 .930 .016 151.68 

4 NDS .965 .932 .002 12.35 

5 W 1,0 .965 .932 .000 -.59 



799 


81** 


80 


58** 


29 


42** 


3 


34 




89 



1 



Letter(s) abbreviations are the following: DM = dry matter; I suffix = 

intake, g/day; OM = organic matter in hay, percent; X suffix = excretion. 

g/day; NDS = neutral detergent solubles in hay, percent; NDF = neutral 

detergent fiber. 
** 

P < .01. 






100 



TABLE 19. 'BEST' FOUR VARIABLE MODELS FOR INDIGESTIBLE NEUTRAL DETERGENT 
SOLUBLES PREDICTION FOUND BY THE MAXIMUM R-SQUARE IMPROVEMENT 
PROCEDURE 1 











Model I 


1 










n 


MEAN 




Value of 


V SE b. 




R 2 


% Y 




Data 


DM I 


OM 


NDFX 


NDS 


P > F 


ALL 


132 


871.81 


.08 
±.01 


-10.45 
±3.53 


.18 
±.03 


1.98 
±1.15 


.94 


12.2 


.0001 










Model II 












n 


MEAN 




Value of 


V SE b. 
1 




R 2 


CVy 

% T 




Data 


DMI 


OM 


NDFX 


NDS 


P > F 


ALL 


132 


1046.4 


.07 
±.01 


-12.39 
±3.63 


.20 
±.03 


2.18 
±1.19 


.93 


12.6 


.0001 



Variables UNDS, DMI, OMI, NDFX expressed in g./day; variables OM, NDS as 
percent of dry matter. 









101 



lower in experiment II (8.4 g/wV°/day) than in experiment I 
(12 9/W k ' /day). Differences in NDF digestibility (40 and 
32% ,. experiments I and II, respectively) may have been an 
important factor, but mainly these results indicate the im- 
portance of plant cell wall constituents in the voluntary 
consumption of forages. There are certain intrinsic charac- 
teristics in the behavior of NDF associated with animal size 
and voluntary intake that are worthwhile mentioning. 

In experiment I, digestibility and absolute intake val- 
ues of NDF were low in young animals (10 months), but in- 
creased markedly from 10 to 16 months. Results from experi- 
ment II showed, however, that animal size, rather than age, 
influences intake. These results might appear contradictory, 
but it is observed (figure 1) that the largest increment in 
body size in animals of experiment I was from 10 to 16 months, 
and corresponded with the stage where significant increments 
in intake of NDF had been observed. On this aspect, Purser 
and Moir (1966) showed that differences between individual 
sheep in voluntary intake were positively related to differ- 
ences in the physiological volume of their reticul orumens ; 
also a direct association between the voluntary intake of 
food and the size of the empty reti cul orumen has been found in 
cattle and sheep (Campling, 1970). In experiment II, highly 
significant correlations were observed between weight of the 
empty digestive tract (DGTW; Appendix table 30) and body 
weight full (r = .94), and body weight empty (r - .96). 






102 



Moreover, across diets NDFI was the forage variable 
most highly correlated (r = .89 and .78, experiments I and 
II, respectively) with body size. 

With a highly digestible diet intake of the NDF frac- 
tion would depend on the amount of OM consumed which, in 
turn, would depend on the animal requirements. With diets of 
low digestibility the i nverse* rel ation would be expected, the 
amount of OM consumed would be determined by the amount of 
NDF consumed, its rate of breakdown and passage from the 
rumen. If it is assumed that in most tropical and sub- 
tropical forages the digestibility of the dry matter is be- 
low the range (65 - 70% digestibility) where physical con- 
trol of voluntary intake appears to cease, then NDF or a 
cell wall constituent would be most likely to play a promi- 
nent role in the amount of forage voluntarily consumed by 
the animal . 

In discussing the results of experiment I it was men- 
tioned that in the low quality Bermuda diet (LQB) the highest 
increase in OM intake (OMI) was from 16 to 22 months (fig- 
ure 4). At 22 months OMI averaged 1400 g/day. A similar 
pattern was observed in animals consuming the Alfalfa diet 
(ALF), but at higher intake levels (2400 g/day at 22 months). 
In the high quality (HQB) the largest increase occurred 
instead between 10 and 16 months when OMI averaged 1730 g/day. 
Calculations of the amounts of NDF consumed at those points 
in the curve showed very similar values: 23.8, 24.3 and 



103 



24.2 g/W k g /day for the LQB, HQ8 and ALF diets respectively. 
Therefore, it seems probable that in the present study the 
amount of feed ingested at different ages was regulated by 
the amount of NDF consumed, its digestibility and rate of 
passage, and the size of the animal. 

Whether the effect of NDF is mediated thru distention 
of the digestive tract or thru the presence of a chemical 
factor (i.e., acetate or acetate: propionate ratio) is un- 
known. The possibility of some form of physical control 
of voluntary intake of ground pelleted roughage through 
distention of the abomasum and intestines has been suggested 
by Campling and Freer (1966) and Campling, Freer and Balch 
(1963). 



Repeatability of Voluntary Intake 



Repeatability of an animal's performance (i.e., the 
amount of milk a cow produces in different lactations, or 
the speed with which a horse runs a race) is an important 
tool utilized by geneticists as an aid to animal selec- 
tion. It also indicates how much is to be gained by repe- 
tition of measurements, and may provide information on the 
nature of the environmental variation (Falconer, 1972). 
Also the repeatability (R) value may be thought of as a 
regression coefficient of one record on another and can be 
used to predict future performance (Turner and Young, 1969) 



104 



In the case of feed intake it is interesting to measure the 
extent to which an expression of intake is likely to be re- 
peated, and the possible implications the repeatability of 
this trait has on prediction of voluntary intake. 

To put this concept into mathematical terms it may be 
approached in a manner similar to that used in animal genetics 
Assuming that repeatability for voluntary intake is .5, what 
would be the most probable vol untary i ntake (MPVI) if the 
same experimental conditions (animal and feed quality) were 
to be maintained? The equation used for this calculation 
has been adapted from that of Lush (1956) which was used to 
calculate the most probable producing ability of a cow: 



MPVI = Iy + 
X k 



n R 
T + (n - 1)R x (I x. " l J. ) > where 

1 K 



Iy - average intake of k number of experimental animals, and 
k 

I-^. = average intake of the i — animal. 

For the purpose of illustration let us assume that 

the average intake of an animal was 10 g/wV°/day, and the 

average intake of all experimental animals was 7 q/wV°/dav 

3 kg ' ; ' 

For a number of records (n) equal to two and a repeatability 
(R) of .5, the MPVI for that animal would be: 



MPVI - 7 + 



2(-5) 



x (10 - 7) 



MPVI = 8.9 g/wV°/d 



Kg 



ay 






105 



Increasing the number of records to four would give 
a MPVI of 9.4, a value which is closer to the true animal's 
average. Thus, by increasing the number of measurements or 
records a gain in accuracy has been obtained. Gain in ac- 
curacy, that is how much more reliable are n number of meas- 
urements than one, may be determined by the following equa- 
tion (C. J. Wilcox, personal communication): 

Gain in accuracy = 1 - [(1 + nR - R) -i n] , 

where n and R are the same as in MPVI. 

Assume a hypothetical example where an animal with n 
number of records consumes an average of 1200 g/day of NDF 
and the average for all experimental animals is 800 g/day. 
The estimated gain in accuracy and MPVI for NDF is shown in 
table 20. 

In summary these calculations demonstrated that, based 
on an R value of .53, the best estimate of intake would be 
at least 212 grams above the all animal mean (MPVI a ), or if 
the animals average of 800 grams per day is maintained then 
the MPVI would be 1012 g/day, when n = 1. By increasing 
the number of measurements to four (n = 4), a 35 percent 
gain inaccuracy of prediction has been achieved and the 
best estimate of intake would be 1127 g/day, closer to the - 
assumed intake value (1200 g/day). 

Falconer (1972) has indicated that increasing the 
number of measurements reduces the amount of variance caused 






106 



TABLE 20. MOST PROBABLE VOLUNTARY NEUTRAL DETERGENT FIBER INTAKE OF 
A HYPOTHETICAL SHEEP, AND GAIN IN ACCURACY OF PREDICTION 
BY REPEATED MEASUREMENTS'! 



Number of 
Measurements 


MPVI a 


MPVI b 


Gain in Accuracy 






g/day 


g/day 


% 


1 




212 


1012 


— 


2 




277 


1077 


23.5 


3 




308 


1108 


31.3 


4 




327 


1127 


35.0 


5 




339 


1139 


37.6 



Sheep averaged 1200 g/day of NDF intake, all estimates based on a 
repeatability of .53. 

Best estimate of animal intake above mean of all animals. 

Best estimate of animal intake when average mean of all animals is 
maintained at 800 g/day. 

Improvement in reliability of estimate compared to estimate based 
on a single record, expressed as percent. 



107 

by temporary circumstances (environmental variance) that ap- 
pears in the phenotypic variance. The reduction in the phe- 
notypic variance represents the gain in accuracy (Falconer, 
1972). Thus, with respect to voluntary intake, where an in- 
crease in accuracy is observed by repeated measurements, the 
amount of variance due to special environment .woul d be ex- 
pected to be as large as repeatability itself, about .47(1-R) 
(Lush, 1956). 

Intake and Body Size 

The exponent relating body weight to voluntary intake 
obtained from these data agrees well with those values re- 
ported by Langlands et al . (1963b), Hadjipieris et al . (1965), 
Greenhalgh and Reid (1973) for sheep, and with Conrad et al . 
(1964) and Taylor and Young (1968) for values concerning 
cattle. In turn, these exponents of body weight are not in 
complete agreement with others reported in the literature 
(table 1 ). 

The interrogant is obvious, why or what causes some 
results to a'gree on a value and others to disagree? A pos- 
sible explanation is that voluntary feed intake is affected 
by many factors, genetic, environmental, quality and availa- 
bility of forage, management practices, physiological state 
of the animal, et cetera , which may have influenced in some 
way the relationship between body weight and voluntary intake. 






108 



Most of the experiments in which a linear relationship be- 
tween intake and body weight has been observed, have one or 
more experimental conditions in common: they have been con- 
ducted with a relatively larger number of animals, over a 
longer period of time, and/or more than one measurement of 
intake have been obtained (Baker, 1964; Conrad, et al . , 1964 
Taylor and Young, 1968). Under such circumstances it is 
most likely that the variability due to environmental dif- 
ferences and physiological state of the animal (i.e., degree 
of fatness, age) which are associated with special environ- 
mental variance (Falconer, 1972) and for which corrections 
have not been made, would be reduced or, ideally, the re- 
lated positive errors would cancel the negative ones. 

As far as forage evaluation is concerned, the problem 
therefore is one of making corrections to standarize those 
conditions or factors unrelated to the forage itself. Vol- 
untary intake, as it is commonly expressed, has many or all 
of those factors associated with environmental variance su- 
perimposed on the variable body size, and consequently any 
change, whether positive or negative, in the effect of those 
factors would be directly reflected upon the value obtained 
as feed intake. 



109 



Intake, Age and Animal Condition 



The results from the regression analysis where fat 
showed a negative effect on DOM intake supports the find- 
ings of other researchers (Bines et al . , 1969; Foot, 1972; 
Graham, 1969; Tayler, 1959). Tayler (1959} reported highly 
significant correlations (r = -.99) between internal fat 
and intake of herbage, and suggested a physical cause for 
this effect; while Bines et al . (1969) did not consider this 
a simple regulatory mechanism. 

In the present study, internal fat was not measured 
as such, therefore no direct conclusion could be drawn. 
However, the animals consuming the high quality diet had 
fatter carcasses although feed intake was considered high 
(0M intake: 37 g/W k * /day), which in a way indicates that 
with high quality pelleted forage diets the possible reduc- 
tion of the abdominal cavity by the accumulation of adipose 
tissue (Bines et al . , 1969; Forbes, 1969; Tayler, 1959) may 
not be a limiting factor on intake, or else that the rate of 
digestion and passage of the high quality diet was fast 
enough to avoid the physical mechanism of rumen fill to be 
a limiting factor. With the low quality diet, on the other 
hand, one would expect slower rates of digestion and passage 
of the ingesta. 

Nevertheless it is important from the experimental 
standpoint that the negative effect of fat on intake gained 



no 



importance with the low quality forage diet. Osbourn et al 
(1970) commented on reducing the animals to a "thin" condi- 
tion before initiating the experiment. Although Osbourn 
et al . (1970) did not elaborate on this aspect it seems evi- 
dent the author referred to the need of avoiding intrinsic 
physiological effects of the animal, such as fatness, to af- 
fect the intake of forages. The results obtained in this 
experiment demonstrate the importance of evading an animal 
condition x diet interaction, particularly when the forages 
under study range widely in quality. Further attention to 
this last aspect is commendable. 



SUMMARY AND CONCLUSIONS 

In experiment I a series of four intake and digest- 
ibility trials were conducted with a group of 24 Suffolk x 
Native crossbred wethers, randomly assigned to one of three 
pelleted forages: a) low qual i ty Coastal bermudagrass 
( Cynodon dactylon ) (LQB) containing 7% crude protein (CP), 
b) high quality Coastal bermudagrass (HQB) containing 14% 
CP, and c) alfalfa ( Medicago sativa ) (ALF) containing 17% 
CP. All diets were offered ad libitum , once daily, for a 
14-day preliminary period and a 7-day collection period. 
The animals averaged 10 months of age in trial I, and 28 
months in trial IV. In experiment II, a group of 36 Suf- 
folk x Native wethers, representing three ages and differ- 
ent sizes within each age, were randomly assigned to two 
pelleted Coastal bermudagrass diets similar in composition 
and quality to the bermudagrass diets used in experiment I. 
Intake and digestibility of diets was measured as in experi- 
ment I. At the termination of the experiment these animals 
were slaughtered and some carcass measurements taken. 

Within diets, digestibility coefficients showed very 
small variability among animals and across diets (c.v.<7%), 
however, changes in digestiblity were observed when deter- 
mined at different times (physiological ages) in the animal. 



Ill 






112 

In experiment I digestibility of the forage diets increased 
with maturity up to 22 months of age, then decreased at 28 
months to a value similar to that observed at 10 months. 
Results from experiment II demonstrated that animal age 
per se does not, however, exert a significant effect on di- 
gestibility of pelleted forage diets. 

Body size, rather than age, determines animal poten- 
tial for forage intake. Young sheep (< 12 months old) do 
not appear to have this potential fully developed especially 
with high fibrous-low quality diets. Small size, however, 
may be the reason for this age effect. Large increments in 
body size corresponded with significant increments in intake 
of NDF, which in turn seems to be closely related to the 
size of the empty reti cul orumen . This assumption is based 
on the high correlations (r = .96) observed between diges- 
tive tract empty weight and body weight, and the findings 
that NDF intake was the intake variable most highly corre- 
lated (r = .89) with body size across all diets. Also in 
both experiments, NDF percentage was the forage parameter 
most highly correlated with intake. 

Repeatability (R) of voluntary intake of pelleted 
forage falls in the upper medium scale of repeatability 
values observed in sheep. Depending on the variable uti- 
lized, R values ranged from .26 to .53. Neutral detergent 
fiber intake per kg of full body weight was the expression 
most highly repeatable (R = .53 ± .10). 






113 



Voluntary intake of pelleted forage diets was more 
related to body weight (W 1-0 ) than to metabolic size (W 75 ) 
For DOM intake the regression coefficient was very close 
to one, and accounted for a highly significant fraction of 
the variation in the logarithm of DOM intake. Similarly, 
the expression of intake that minimized the effect of body 
weight on intake was grams of DOM per W *°. In this expres- 
sion, body weight accounted for not more than four percent 
of the variation in observed intake. 

Multiple regression analysis of the independent 
variables body weight, age, and carcass fatness on intake, 
showed that body weight exerts a highly significant posi- 
tive effect on DOM intake whereas age does not seem to play 
a significant role. Carcass fatness, however, showed a 
negative effect .on DOM intake regardless of forage quality, 
but its effect gained importance with the low quality for- 
age diet. This last aspect should be further investigated 
since it could affect the usefulness of intake as an index 
of forage quality. 



APPENDIX 



115 



i — i 



Q 
CO OO 

Cx> 

re +1 
i- 

o c 

U_ ro 
CO 



LU 
CD 

< 



LU 
Q2 

u. 



lo 



(— 

rro 



LU 



>- 

< 



Q 

< 

>■ 

i— i 

_J|— 

i— iZ 
CO LU 



cooi 

LULU 

csa. 

MX 
Q LU 



CM 






CO 

CM 



o 



UJ 

CD 



CM 
CM 



«3 



a; 



5- 



co 

C\] 


CM 


CSJ 

co 


+1 


+1 


+1 


X 


CO 




o 
<3- 


LO 


uo 



Ps 


f- 


CT> 


• 


« 


* 


ro 


CO 


«*• 


+i 


+1 


+! 


X 


>> 


N 


T— 


I 


r^ 


> 


■ 


• 


o 


CO 


LO 


«5f 


LO 


«*■ 



o 

J3 J3 J3 

cm ^t- en 



u 

X! JO 



JQ 
O 



cm r^. 
>=j- LO 



LO 



LO 



LO 



LO 






(0 ra 
LO CO 


re 


CVJ 


ra 

LO 


co 


ra 

LO 


CM 


CO LO 


CO 

LO 


CT) 


LO 

■ro 


en 


«d- 


CM 



co ai lo 

CM "3- LO 
CM CO "3" 



+1 +1 



< 


>) 


N 


CJ1 


CM 


«* 


en 


r-~ 


co 


CM 


co 


r— 



3 


<a 


fO 




.a .a 


f0 








LO 


o 


LO 


o 


C7l i— 


CO 


en 






• 


• 


• 


• 


« ■ 


• 


• 


-O "O X> 




CD 


LO 


CO 


o 


en cm 


CM 


>st 


LO CO CO 


O 


«t 


LO 


LO 


LO 


CO LO 


„j. 


*f 


CO LO CO 
>* i— LO 
1— CM CM 


CTi 

O 

CM 



o 


o 


u 




O 


o 


o 










<* 


o 


o 


r— 


<d- 


o 


^t- 


en 








" 


• 


• 


• 


■ 


• 


• 


• 


-Q 


o 


(_> 


CO 


o 


Ch 


"* 


co 


r-- 


C\J 


o 


C31 




r-~~ 


■=3- 


LO 


LO 


LO 


<- 


LO 


LO 


LO 


CO 

co 


CTi 


OT 
CO 

CM 



en 
en 



« -Q JO 

CT) tsd" VO CO 

CM CO CO CO 

N N rji «3 



rO re fC 

CO O O i— 

cri ai n in 

O CO LO CO 



-s~> 



4-s 
to 

tti 



s. 






GJ 






+J 






+J 






ra 






s: 


CM 






CQ 


CO 


u 


o- 


CD" 


'1 — ' 


_J 


T 


c 






ra 






en 






i. 






O 









•M 








c 








CD 








en 








s- 








aj 






C 


-i_> — . 






(C 


CD Li_ 






QJ 


O Q 






E 


2: 


CO 


CO 




r— * — " 


CT 


err 


CD 


ns 


_J 


~~ 


en 


J- S- 






< 


Neut 
Fibe 











cu 










+-> 






c 


> 


4-> 






ro 


(0 


« 






CO 


"O 


?>" 






E 






CQ 


CO 




CT 


o 


err 


err 


a> 




•p™ 


i 


re 


OM 


r 


c: 






<C 


CO 

ra 


ra 

CJ) 

o 







ra 

O) 



aj 

CT) 






116 







































00 








































to 






































fC 






































i- 








































en 








































ro 








































-D 




• 








i — 


o 


lo 






r-. 


On O 






CM 


CM 


CI 






3 
E 




LO 




Q 




co 


1* 


«*■ 






o 


en to 






en 


•=*• 


co 






L. 




o 




CD 1/5 

CD 

ro +i 




+i 


CM 
+1 


CM 

+1 






+1 


i— CM 
+1 +1 






+1 


+1 


+1 










• 

V 




o c 




X 


rsi 


>^ 






X 


>, n 






X 


N 


>, 






r— 
rC 




Q 




Li_ rO 




CO 

LO 


CD 

in 


o 

LO 






LO 
CO 


LO "3" 

oo r-^ 






o 

CO 


LO 

LO 


CO 

CO 






4-i 
00 


• 






E 




o 


CM 


< — 






lo 


O r— 






<* 


LO 


LO 






co 


LO 


+J 












! ' 








r— r— 

• 
















o 
CJ 

•p- 


o 

V 

o_ 


re 
O) 
S- 

CD 

c+- 

'1 — 
T3 






































z> 


4-J 












cj 


■o 


-o 






CJ 


o -o 






o 


CJ 


oo 






o- 


CO 


■OJ 






CO 




LO 


CM 


o 


lo 




CM 


r— CO 


LO 




en 


en 


r-~ 


CM 




_cc 


s_ 


rtJ 






CM 




OJ 


CO 


CM 


i — 




o 


CO CO 


LO 




co 


LO 


o 


CM 




CD 


CL) 












CM 


«* 


itf 


CO 




LO 


i— CO 


o 




«S" 


r~~ 


LO 


LD 




-: — 


4- 


oo 




































00 

c: 
o 

+-> 


re 
n 

CO 

o- 
re 


•P™ 

CD 
ro 


+J 

OL 

L 
o 

00 

£- 
0) 










CJ 


























(0 


* ^ 


oo 


CL 










JO 


cj 


U 






o 


(_> CJ 






o 


o 


CJ 




> 


^--^ 


4-> 


3 






CM 




r--. 


•3- 


<T> 


O 




CO 


CM i— 


LO 




o 


r-. 


LO 


r>. 


i- 


c 




o. 


00 






CM 




CM 


"s* 


O 


to 




o 


CO i— 


LO 




en 


LO 


CO 


«=}- 


cu 


o 
















i — 


CO 


CO 


OJ 




LO 


i— sl" 


o 




«* 


r-. 


LO 


LO 


L0 






>_ 


4J> 




00 
JO 

+J 

o 

E 






' 


1 — 


■ — 


' — 






r— i — 


1 — 












JO 


>! 




a 


re 


































o 


+-> 




00 


CJ 




































o 




S-. 


S- 


































+-> 


ro 




a 


CJ 


































JC 


T3 




D. 


<+- 


































CD 






3 


4- 




" 


































ro 
O 




oo 


'i — 

-a 




LaJ 

O 






(0 


JO 


JO 






JO 


JO JO 






JD 


JO 


4D 




o 


■a 

o 




4J 

ro 

CD 


CD 




eC 


LO 




LO 


I — 


O 


en 




r~~ 


LO CM 


co 




i — 


r— 


r~- 


co 




>- 




5- 


•r™ 






f ~"' 




! 


CM 


LO 


Ol 




i" - 


CD. LO 


LO 




CM 


LO 


co 


CM 


c 


C_5 




ai 


J_ 










O 


CM 


CD 


o 




lo 


on o 


co 




«* 


LO 


<d- 


LO 


« 




<-:- 


ro 












i — 




r — 




















CD 

E 

CJ 

-CC 

+-> 

00 
4-> 

C 


nudagrass 
a). 


4- 
■I — 
"O 

CD 

re 

i- 
ro 
CD 


CO 
JO 

00 

re 
ro 

CO 

E 
CD 






O 




CO 


re 


CO 






ro 


<T3 rC 






ITS 


CO 


ro 




a> 


S- > 


JO 


CD 








lo 


r— 


; — 


Cvi 




en 


CM CO 


i — 




en 


CO 


CO 


O 


00 


CD -r- 




ro 






r ~~ 




o 


uo 


lo 


CD 




; — 


CO «* 


CO 




! 


LO 


lo 


CO 


CD 


JO 4-> 


^ 


S_ 








en 


en 


CO 


0~i 




^r 


I s * co 


LO 




CO 


«tf- 


CO 


CO 


cx 

CJ 


CO 
i — 00 

+-> O 


o 

L- 

CJ 


o 
4- 


-a 

CD 

=5 






















**"*» 












oo cn 


£ 


ro 






















ll_ 










0) 


rO ro 


ro 


o 














- « 








CD 










Z5 


O CJ 


oo 
















s: 








s: 










pMl 


O -r- 




s_ 


C 




■M 










o 








CD 










ro 


■a 


CD 


CJ 


+-> 




re 










— - 








' — ' 










> 


>, CD 


JO 


4J> 

*! 


sz 




Cn 


















Li_ 










CD 


<l — <^^* 




i_ 


o 




i- 










s: 








CD 










CD 


, 


E 


i_> 


C_> 




cu 










o 








z: 










(B 


ro ro 


•l — 




i 


rC 










C 

re 


OJ 






c 
to 


0) 










1 

CU 


CD"i — 


00 


ro 




•I— 


Q CD 








CJ 


i — 






cu 


^— 








a> 


CD 


CO 


re 


ro 


, 


£_ 


z: 


CQ 


CQ 


u_ 


E 


-Q 


ca 


CO U_ 


£ 


-Q 


CQ 


CO 


Ll_ 


E 


ra 


2 4- 


ro 


•i — 


CM 


CU 


r - ••— ' 


o* 


cr 


1 




"r — 


o- 


CD- — 1 




•i — 


o- 


cy 


| 




S- 


O i — 


CD 


jr 


+J 


CO 


1 


CO 


<C 


CJ 


4_? 


_j 


en < 


CJ 


4-J 


! 




< 


<u 


o 


—i <C 




+J 




" r— 


i- i~ 








en 


00 






CD 


00 








CD 


4- 




"O 


•i — 




£• 


4-J O) 








< 


OJ 






<c 


OJ 








<£ 




II II 




3 


cu 


CD 


3 -Q 










en 








en 










J= 




CJ 


N! 


r— 




a) •!— 










-i — 








•r— 










(_) 


CO u_ 






JO 


Z U ~ 










Q 








CD 










"3 


CD-—I 


JO 


>^ 


j 




























LU 


—I <c 


« 




r^ i 


































— CM 




ro 


X 



117 



TABLE 22. VOLUNTARY INTAKE OF DIGESTIBLE ORGANIC HATTER AND NEUTRAL 
DETERGENT FIBER EXPRESSED AS FUNCTIONS OF BODY WEIGHT AND 
METABOLIC SIZE ACROSS AGES. EXPERIMENT il 





Criteria 




Age, months 




Foi 

mean 


'age 


10 


16 


22 


28 


± SD 


Intake, g/W^/day 














Digestible OM (DOM) 














LQB 2 


11. 9 a 


11. 7 a 


12. 7 b 


11. 7 a 


12. O x 


± 1.1 


HQB 


20.7 ab 


19.8 ab 


21. 2 b 


19. 6 a 


20. 3 y 


± 1.9 


ALF 


22. 9 a 


21. l a 


26. b 


23. O a 


23. 3 Z 


± 2.6 


Digestible NDF (DNDF) 














LQB * 


9.2 a 


9.5 a 


10. 3 b 


9.5 a 


9.6 X 


± .9 


HQB 


12.4 ab 


13.1 ab 


13. 8 b 


12. 8 a 


13. Z 


± 1.3 


ALF 


9.6 a 


9.7 a 


12. 6 b 


10. l a 


10. 5 y 


± 1.5 


Intake, g/W^ 5 /day 














Digestible OM (DOM) 














LQB 


28. 8 a 


30. 2 a 


33. 3 b 


31.4 ab 


30. 9 X 


± 3.1 


HQB 


51. 4 a 


52. 7 a 


57. 9 b 


54.7 ab 


54. 2 y 


± 5.3 


ALF 


56. 4 a 


56. 2 a 


70. 6 C 


64. l b 


61. 8 Z 


± 7.8 


D; jestible NDF (DNDF) 














LQB 


22. 3 a 


24. 6 b 


27. 1 C 


25. 5^ 


24. 9 X 


± 2.8 


HQB 


30. 8 a 


34. 9 a 


37. 6 b 


35. 6 a 


34. 7 2 


* 3.9 


ALF 


23. 6 a 


25. 8 a 


34. 3 C 


28. l b 


27. 9 y 


± 4.6 



Each forage-age value represents the mean of eight observations. 
2 
See table 2 for description of forages. 

a ' Means in the same row bearing different superscripts are different 

(P < .05). 

x y z 
'••" Within a criterion, forage means bearing different superscripts 

are different (P < .05). 



118 



TABLE 23. CORRELATION MATRIX OF SELECTED FORAGE EVALUATION PARAMETERS. 
EXPERIMENT I 1 



Item 2 


OM 
(%) 


NDF 
(%) 


NDS 
(X) 

.25 


DMD 
(%) 

.37 


OMD 
(%) 

.37 


IVOMD 
(%) 

.31 


NDFD 


DOM 


DNDF 
(%) 


UNDS 
{%) 


BW 75 (kg) 


-.28 J 


-.26 


.46 


.35 


.11 


.38 


BW IU (kg) 


-.28 


-.26 


.26 


.36 


.36 


.32 


.45 


.35 


.10 


.38 


NDFX (g/d) 


-.00 


.03 


-.04 


-.23 


-.24 


-.12 


-.23 


-.27 


-.14 


.23 


OMX (g/d) 


-.45 


-.42 


.26 


.13 


.12 


.26 


-.03 


.03 


-.41 


.63 


DMX (g/d) 


-.55 


-.52 


.51 


.23 


.21 


.36 


.03 


.12 


-.47 


.69 


DNDFI (g/d) 


-.24 


-.26 


.26 


.62 


.56 


.49 


.77 


.57 


.35 


.16 


DOMI (g/d) 


-.75 


-.77 


.77 


.78 


.78 


.80 


.45 


.35 


.10 


.62 


DDMI (g/d) 


-.79 


-.80 


.80 


.78 


.78 


.81 


.58 


.71 


-.31 


.66 


NDFI (g/d) 


-.16 


-.16 


.15 


.30 


.30 


.27 


.40 


.31 


.16 


.23 


OMI (g/d) 


-.70 


-.69 


.69 


.59 


.59 


.65 


.41 


.51 


-.33 


.93 


DMI (g/d) 


-.75 


-.74 


.73 


.60 


.60 


.68 


.39 


.52 


-.39 


.94 


DNDF m 

+NDS u ° ; 


-.76 


-.79 


.81 


.98 


.98 


.93 


.82 


.95 


-.10 


.50 


UNDS (55) 


-.85 


-.82 


.80 


.37 


.36 


.52 


.05 


.21 


-.72 




DNDF (%) 


.71 


.68 


-.67 


-.04 


-.02 


-.31 


.46 


.14 






DOM («) 


-.55 


-.61 


.62 


.98 


.98 


.86 


.91 








NDFD (%) 


-.28 


-.33 


.34 


.84 


.86 


.63 










IVOMD (35) 


-.82 


-.86 


.86 


.93 


.92 












OMD {%) 


-.69 


-.73 


.74 


.99 














DMD (%) 


-.69 


-.74 


.75 

















Animal observations = 96. 

Letter(s) abbreviations are the following: OM = organic matter- NDF = 
neutral detergent fiber, ash-free; NDS = neutral detergent solubles a^h- 
free; DM = dry matter; D suffix ■ digestibility (%); IVOMD = in vitro 
OMD; D prefix = digestible {% of dry matter); U prefix = undi^estTbTe 
U of dry matter); I suffix = intake (grams/day); X suffix = excretion 

(grams/day); W ' = metabolic size (kg); w 1,0 - body weight (kg); values 
without suffix or prefix are composition as % of dry matter. 

Linear correlation coefficient (r); levels of significance: 1% if 
r > .26, 5% if r > .20. (Snedecor and Cochran, 1967). 






119 



Table 


23 - 


Extended 
















DNDF 




















— 


+NDS 
{%) 

.43 


DM I 

(g/d) 

.75 


OMI 

(g/d) 

.78 


NDFI 

(g/d) 


DDMI 

(g/d) 


DOMI 

(g/d) 


DNDFI 

(g/d) 


DMX 

(g/d) 


OMX 

(g/d) 

.74 


NDFX 

(g/d) 

.65 


BW L0 
(kg) 


.88 


.69 


.71 


.82 


.73 


.99 


.42 


.75 


.78 


.89 


.69 


.71 


.82 


.74 


.74 


.65 




-.18 


.55 


.59 


.79 


.34 


.35 


.41 


.81 


.88 






.22 


.85 


.86 


.80 


.69 


.68 


.52 


.99 








.31 


.90 


.91 


.77 


.76 


.75 


.53 










.63 


.71 


.75 


.89 


.75 


.79 












.83 


.96 


.96 


.71 


.99 














.83 


.97 


.96 


.68 
















.34 


.76 


.80 


















.66 


.99 




















.68 


























120 



TABLE 24. LOGARITHMIC REGRESSIONS OF INTAKE VARIABLES (Y) ON BODY 
WEIGHT (X). EXPERIMENT il 



Intake Variable 
(g/day) 


n 


b 


b i 


+ 


S h 


S 

y.x 


R 2 


P > F 


Dry Matter (DM) 


















LQB 2 


32 


1.73 


.85 


+ 


.09 


.039 


.75 


.0001 


HQB 


32 


1.74 


.90 


+ 


.08 


.041 


.78 


.0001 


ALF 


32 


1.59 


1.04 


+ 


.08 


.043 


.82 


.0001 


Organic Matter (OM) 


















LQB 


32 


1.74 


.83 


+ 


.09 


.039 


.73 


.0001 


HQB 


32 


1.73 


.89 


+ 


.09 


.041 


.77 


.0001 


ALF 


32 


1.56 


1.04 


-r 


.09 


.043 


.82 


.0001 


Neutral Detergent 
Fiber (NDF) 


















LQB 


32 


1.68 


.82 


+ 


.09 


.039 


.73 


.0001 


HQB 


32 


1.56 


.90 


+ 


.08 


.040 


.78 


.0001 


ALF 


32 


1.29 


1.04 


+ 


.08 


.042 


.82 


.0001 



Log-jg Y = b Q + b-j (Log-^ X); b, = standard error of regression coeffi- 

S 2 

cient; y.x ■ standard error of estimate; R = coefficient determination. 

See table 2 for description of forages. 



121 



TABLE 25. POOLED WITHIN AGES LOGARITHMIC REGRESSIONS OF INTAKE VARIABLES 
(Y) ON BODY WEIGHT (X). EXPERIMENT I 1 



Intake Variable 
(g/day) 


n 


b O 


b l * S 


Vx 


R 2 


P > F 


Dry Matter (DM) 














2 

LQB^ 


32 


1.47 


1.01 ± .16 


.037 


.79 


.0001 


HQB 


32 


1.93 


.79 ± .24 


.042 


.79 


.0001 


ALF 


32 


1.87 


.89 ± .23 


.038 


.88 


.0001 


Organic Matter (OM) 














LQB 


32 


1.46 


1.00 ± .16 


.037 


.78 


.0001 


HQB 


32 


1.90 


.79 ± .24 


.042 


.79 


.0001 


ALF 


32 


1.82 


.89 ± .23 


.038 


.88 


.0001 


Neutral Detergent 
Fiber (NDF) 














LQB 


32 


1.38 


1.00 ± .16 


.037 


.78 


.0001 


HQB 


32 


1.73 


.80 ± .24 


.042 


.79 


.0001 


ALF 


32 


1.56 


.88 ± .23 


.038 


.87 


.0001 


Digestible OM (DOM) 














LQB 


32 


1.04 


1.02 ± .17 


.039 


.83 


.0001 


HQB 


32 


1.81 


.70 ± .24 


.041 


.80 


.0001 


ALF 


32 


1.32 


1.03 ± .23 


.037 


.89 


.0001 


1l °9i0 Y = b O I b ] ( 
coefficient; y.x = 


-og 10 x) 4 


• b 2 AGE ; 


s 

b, = standarc 


error 


of regression 


standard 


error of 


2 

estimate, R = 


coeff 


icient 


of 



determination. 
2 
See table 2 for description of forages. 



122 



TABLE 26. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR THE COMMON 
LOGARITHMIC REGRESSION OF INTAKE VARIABLES (Y) ON BODY WEIGHT 
(X). EXPERIMENT I 1 



Intake Variable 
(g/day) 


n 


b O 


b l ± \ 


S 

y.x 


R 2 


P > F 


Dry Matter (DM) 


96 


1.65 


.96 ± .11 


.039 


.92 


.0001 


Organic Matter (OM) 


96 


1.62 


.96 ± .11 


.039 


.91 


.0001 


Neutral Detergent 
Fiber (NDF) 


96 


1.44 


.96 ± .12 


.040 


.82 


.0001 


Digestible OM (DOM) 


96 


1.37 


.93 ± .11 


.039 


.95 


.0001 



Log 1Q Y = b Q + b 1 (Log 10 X) + b 2 FORAGE + b 3 AGE: S b ] = standard error 

of regression coefficient; s y.x. = standard error of estimate, R 2 = 
coefficient of determination. 



123 



TABLE 27. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR TRE LINEAR 
REGRESSION OF INTAKE PER KILOGRAM BODY WEIGHT (W?-0) (Y) ON 
BODY WEIGHT (X). EXPERIMENT I 1 k 9 



Neutral Detergent 
Fiber (NDF) 

L Q B 32 28.55 -.098 ± .050 2.14 .119 



1 S 

Y = b Q + b-jX; b-j = standard error of regression coefficient; S y.x 

standard error of estimate; R" = coefficient of determination. 

See table 2 for description of forages. 



Intake Variable 


















(g/wj g °) 


n 


b 


b l 


+ 


b l 


S 

y.x 


R 2 


P > F 


Dry Matter (DM) 


















LQB 2 


32 


35.24 


-.101 


+ 


.060 


2.69 


.084 


.110 


HQB 


32 


41.90 


-.068 


+ 


.070 


3.54 


.032 


.323 


ALF 


32 


40.82 


.037 


+ 


.091 


4.69 


.006 


.679 


Organic Matter (OM) 


















LQB 


32 


34.25 


-.109 


+ 


.060 


2.59 


.100 


.070 


HQB 


32 


39.24 


-.071 


± 


.060 


3.28 


.040 


.270 


ALF 


32 


40.97 


.027 


+ 


.081 


4.23 


.004 


.740 



.052 



HQB 32 26.95 .047 ± .041 2.22 .038 .282 

ALF 32 22.37 .013 ± .040 2.26 .003 .767 



124 



TABLE 28. REGRESSION COEFFICIENTS AND STATISTICS OF FIT FOR THE LINEAR 
REGRESSION OF INTAKE PER KILOGRAM OF METABOLIC SIZE (W' 75 ) (Y) 
ON BODY WEIGHT (X). EXPERIMENT I 1 Kg 



Intake Variable 



<9< 5 > 


n 


b O 


b l 


+ 


S h 

b l 


S 


R 2 


P > F 


Dry Matter (DM) 


















2 
LQB 


32 


71.06 


.180 


± 


.150 


6.83 


.043 


.252 


HQB 


32 


84.62 


.345 


± 


.181 


9.50 


.107 


.067 


ALF 


32 


88.64 


.756 


± 


.240 


12.34 


.254 


.003 


Organic Matter (OM) 


















LQB 


32 


69.28 


.143 


± 


.150 


£.56 


.029 


.343 


HQB 


32 


79.46 


.301 


± 


.169 


8.80 


.096 


.085 


ALF 


32 


79.42 


.655 


± 


.212 


11.11 


.240 


.004 


Neutral Detergent 
Fiber (NDF) 


















LQB 


32 


57.93 


.096 


± 


.120 


5.39 


.020 


.435 


HQB 


32 


54.60 


.212 


± 


.110 


5.98 


.102 


.075 


ALF 


32 


43.47 


.351 


± 


.110 


5.95 


.240 


.004 



1 S s 

Y = bg + b.|X; b, = standard error of regression coefficient; y.x 

standard error of estimate; R = coefficient of determination. 
2 
See table 2 for description of forages. 






125 



TABLE 29. AGE AND FORAGE QUALITY EFFECT ON VOLUNTARY INTAKE , 
EXPRESSED AS FUNCTION OF BODY WEIGHT. EXPERIMENT II 1 









AGE, months 




Forage 
mean ± SD 


Criteria 


12 


24 


36 


Organic Matter 


(OM) 




• 






LQB2 2 




24.2 


26.8 


22.7 


24. 6 a ± 3.9 


HQB2 




36.4 


38.0 


36.6 


37. b ± 3.2 


Age mean 




30.3 


32.5 


29.7 




Neutral Detergent 
Fiber (NDF) 










LQB2 




19.7 


21.8 


18.5 


20. O a ± 3.2 


HQB2 




24.1 


25.2 


24.3 


24. 6 b ± 2.1 


Age mean 




21.9 


23.5 


21.4 




Digestible OM 


(DOM) 










LQB2 




8.1 


9.6 


7.9 


8.4 a ± 1.2 


HQB2 




21.6 


22.1 


21.3 


20. 7 b ± 1.5 


Age mean 




14.3 


15.2 


14.0 




Digestible NDF 


(DNDF) 










LQB2 




6.1 


7.3 


5.9 


6.4 a ± 1.0 


HQB2 




12.8 


12.8 


12.6 


12. 8 b ± 1.1 


Age mean 




9.4 


10.1 


9.2 





1 1 

Grams/W * /day; each forage-age value represents the mean of six obser- 
vations. y 
2 
See table 11 for description of forages. 

' Within a criterion, forage means bearina different superscripts are 
different (P < .05). 



126 



Q 

UJ S^ 
t — l ' 

>- 



a. 

X 

UJ 



00 

d 

UJ 

h- 

LU 

s: 
<c 
or 

< 
tx 

O0 

< 

o 

< 

Q 

UJ 

o 

LU 
_J 
LU 
CO 

u. 
o 

X 

w 



Q UJ 
_J Q 

UJ cC 
i— i CC 
>- CD 



CD- 



>- h- 

UJ <'-~ 

■z. u_ &s 

Q 

M + 

NX 

LU 
>- 



U_ UJ • 



CQ UJOJ 

>-■ >- £ 
ex: uj o 



LU 

or: 

a 

o 
o 



o 

CO 

UJ 
_' 

CQ 

<c 



CO 

CO 

OS 

< 






■— CO 

r--. cti 






co 

CD 



co 



LO 
LO 



o 

CO 



co 

LO 



co cr> 



cr> lo 



CO 



CPl l£i 



CO CM 

CO <■ 



CO 

LO 



O 



CTl CO r— Csj CO CO 

co co co co co r-^ 



T3 



T3 

c 
res 

o 

ST. 



II 



E 
ra 

S- 

CJ> CD 



LO 
CV! 

CO 



A| 



CJ 



O 4- 



-o J*: &s 

c en 
re c 

■r— ■* 

3 CO 

Or— r— 

I— i— «3- 

O <C 



• * 4-1 
>,J^ 

r— en 

> O) 
i- 2 
4J 

O -M 
CD O 
CL ra 
(/) £- 
CD 4-> 
S- 

« > 

CD V) 
•i— CD 

<D cn 

2 f- 
•o 

>> 
-a •>, 

O 4-> 

JO CL 



A| 



3rS 



CO 
U 

c 

ra 
O 



c 

CD 







127 



TABLE 31. CARCASS CHARACTERISTICS OF THE EXPERIMENTAL ANIMALS 
EXPERIMENT II 1 







AGE, 


months 




Forage 
mean ± SD 


Criteria 


12 


24 


36 


Body Weight, 


Full (kg) 










LQB2 2 




41. l a 


41. 9 a 


54. 8 b 


45. 9 X ± 8.6 


HQB2 




48. 6 a 


47. 3 a 


62. 9 b 


52.^ ± 9.5 


Body Weight, 


Shrunk (kg) 










LQB2 




38. 8 a 


39. 3 a 


51. 7 b 


43. 3 X ± 8.3 


HQB2 




45. 5 a 


44. 4 a 


58. 9 b 


49. 6 y ± 8.9 


Body Weight, 


Empty (kg) 










LQB2 




31. 9 a 


30. 9 a 


41. 7 b 


34. 8 X ± 7.0 


HQB2 




39. 6 a 


39. a 


50. 4 b 


43.0^ ± 7.5 



Digestive Tract 
Weight, Empty (kg) 



LQB2 


3.8 a 


3.4 a 


4.9 b 


4.0 X ± .9 


HQB2 


4.8 a 


4.8 a 


6.1 b 


5.3 y ± .9 


Carcass Weight, Hot (kg) 










LQB2 


18. 8 a 


18. l a 


25. 4 b 


20. 8 X ± 4.7 


HQB2 


23. 6 a 


22. 9 a 


30. 6 b 


25. 7 y ± 5.0 


Carcass Weight, Chilled (kg) 










LQB2 


18. 5 a 


17. 7 a 


24. 8 b 


20. 3 X ± 4.6 


HQB2 


23. l a 


22. 4 a 


30. l b 


25. 2 y ± 4.9 


2 
Rib Eye Area (cm ) 










LQB2 


11. l b 


10. 7 a 


9.2 a 


10. 4 X ± 1.8 


HQB2 


10. 2 a 


9.7 a 


8.9 a 


9.6 y ± 1.2 






128 



Table 31 - Continued 







AGE, months 




Forage 
mean ± SD 


Criteria 


12 


24 


36 


Fat Over Eye 


(mm) 










LQB2 




2.1 a 


1.9 a 


4.5 a 


2.8 X ± 2.7 


HQB2 




4.5 a 


4.7 a 


5.8 a 


5.^ ± 1.5 


Yield Grade 












LQB2 




2.2 a 


2.2 a 


3.2 b 


2.6 X ± .9 


HQB2 




3.3 a 


3.1 a 


3.6 a 


3.3 y ± .7 


Yield {%) 












LQB2 




46. 8 b 


46. 8 b 


45. a 


46. 2 X ± 1.7 


HQB2 




44. 9 a 


45. 2 a 


44. l a 


44. 7 X ± .9 


Kidney + Kid 


ney Fat (%) 










LQB2 




2.1 a 


2.1 a 


3.4 b 


2.5 X ± .9 


HQB2 




3.6 b 


2.7 a 


3.4 b 


3.3 y ± .7 


Leg {%) 












LQB2 




30. 3 b 


29.7 ab 


28. 6 a 


29. 5 X ± 1.3 


HQB2 




29. 6 b 


2g 2 


27. 9 a 


28. 9 X ± 1.2 


Carcass Fat 


{%) 










LQB2 




27. 9 a 


28. 7 a 


33. 5 b 


30. l x ± 4.3 


HQB2 




31. 9 a 


32. 3 a 


35. 5 a 


33. 2 y ± 2.9 


Carcass Lean 


[%) 










LQB2 




56. 7 b 


56. l b 


52. 4 a 


55. l y ± 3.2 


HQB2 




53. 6 a 


53. 5 a 


51. a 


52. 7 x ± 2.2 



Within a criterion, forage means bearing different superscripts 
are different (P < .05). 



Each forage-age value represents the mean of six observations. 
See table 11 for description of forages. 

Means in the same row bearing different superscripts are 
differnet (P < .05). 









129 



LU 
SI 

I — i 

or: 

LlJ 

ex 

X 

UJ 



J— 
< 

Q 

LU 

< 






ca 



to 

LU 
CD 



o 

LL 

LU 

o 



> 

o 
to 

I — I 
C/0 

>■ 
< 
< 
00 

LU 
QC 
< 
-O 

cr 



1/3 

< 

LU 



Cm 



LU 



Cfi 
< 



S- 

c 

•1 — 

re 

E 
QJ 



a; 
< 



CD 

en 
re 
S- 

o 

LU 



1 — 1 


en 


CxL 


ro 


<£ 


i- 


>■ 







Ll_ 


u. 


■^-* 





CL 




<L) 


LU 


O) 


C_) 


x: 


q: 


00 


_D 




O 




00 





CD 
CD 

< 



CD 

CD 

tO 

i- 

o 

LU 



CD 
+-> 

S- 

o 



CD 



CM CO ^t- 1— «* 

co cm cn oo co 

co cm co 1 — r-» 

CO LO CO CM LO 



CM 



LO CM CM 



.£5 rC JO. re 

lo r-. lo en co 

lo co o 1— en 

en CM LO r— en 

lo r-. lo co 00 



co LO 

■3- 1— 



en lo cm 



o 
en 



CM CM CM 

o r-» co 

O O en 

CO 1— LO 



CD 
CO 



co 



00 



re 


re 


re 


re 


re 


en 


r— 


CM 


LO 


m 


«*■ 


CO 


LO 


LO 


CO 


«tf- 


ID 


CO 


CD 


00 


cn 


CM 


C) 


co 


O 


CO 


O 


r— 


CM 


=T 


CO 


«*• 





CM 


, 


1 — 


CO 


1 — 


1 — 





hs 



"3- 



<* LO 
LO LO 



«*■ CM CO CM CM 

o O lo en r-» 

en o «a- co r-~ 

r--. cn uo cm 00 



re 

O rC JO. 

re ro O LO "5J- 

lo o r-- co lo 



r*s 


en 


00 


1 


CO 


r-- 


a) 


co 


r*. 





en 


Cvi 


en 


m 


1 — 


LO 


"ST 


LO 


CO 


CO 


CO 


CO 


CD 


1 — 


1 — 









ro 


ro 


ro 


rd 


ro 


CM 


LO 


LO 


LO 


LO 


CX! 


CD 


CM 


LO 


O 


*fr 


LO 


I-- 


r— * 


f-. 


Cn 


1 — 


LO 


CO 


<=+ 


r^ 


cn 


r— 


1 — 


LO 


CO 


CO 


cn 


*t 


CXI 




1 — 









ro 


ro 


re 


ro 


ro 


1-^ 


CO 


CM 


CM 


cn 


O 


co 


, — 


CM 


. — 


LO 


__ 


O 


O 


00 


LO 


too 


LO 


CO 


r-~ 


"* 


r*. 


UD 


CO 


CD 


CO 


LO 


CO 


r 


O 


LO 


CO 


LO 


O 


CO 


CO 


CM 


CM 


1 









ro 


ro 


rtS 


rd 


ra 












r-. 


CO 


CO 


-sf 


<sr 












O 


CM 


f* 


LO 


a-, 








ro 




LO 


1 — 


CM 


LO 


CD 


rO 


ro 


ro 


LO 


CO- 


<=r 


' — 


P-* 


«* 


cn 


co 


CO 


["••» 


co 


CM 


CO 


, 


i-> 


LO 


r-~ 


r— 


CO 


CO 


<r 


^7- 


r— 


CO 


CXi 


CO 


CO 


CO 


cn 


<*■ 


r-» 


<=}■ 


CO 


CO 


LO 


CXi 


1 


uo 


LO 


r-» 


<3" 


r — ■ 


CM 


.— 


( — 


1 — 




co 


CM 





00 


r~. 












r~- 


LO 


CO 


<~ 


CM 












LO 


CM 


CD 


<lr 














UO 




CO 







■a 


4-> 
C 
CD 












ra 
XJ 

in 








(— ! 






O 




O 




LU 


LO 


F 




1 — i 


(— ! 


LL 


X 




i_ 


Q 


u. 


> 


a 


Q 


ra 


*■ — i 


u_ 


?~ 


a 


Li. 




CO 


2l 


LJ 





z 


Z 


£- 


s: 


Q 


O 


z 


ro 




o_ 


O 


z 


a 


Q 


no 


CD 





sr 


Cj 





z 






130 



-a 

OJ 



c 
o 

CO 



CNJ 
CO 



CO 



X2 



S- 
<V 



a: 



CD 

en 



cn 
rO 

C_ 

o 



< 


CO 


I — 1 


CD 


Qt 


CO 


< 


s- 


> 


o 




LL. 


U_ 


*»_ 


O 


Cl 




CD 


UJ 


CD 


o 


sz. 


or 


LO 


rD 




o 




CO 





CO 

ld 



lo 



CD 
CO 



CD 

cn 

(0 

i- 
o 



to 
+j 

L 
o 



4- 





cn 




cn 


LO 




Lf) 




"vl- 


cn 


Ol 


LD 


oo 


LO 


CNJ 


r — 


*3" 


vr 


LO 


oo 


oo 


r-- 


i — 


«5f 


r-^ 


CO 


CJ 


0) 


r-. 


cn 





rd 




cO 


JD 




i_n 




CO 


r^. 


_o 


«*■ 


ta 


: 


i — 


■sj- 


1 


LO 


V) 


^— 


■et 


** 


! 


LO 


sf 


i — 


<=r 


CO 


CNJ 


CM 


CSJ 


cn 


l-N, 


LO 


CXi 



<* ID iD CM W 





CO 




(T3 


CO 




CO 




i-«. 


CO 


CO 


o 


<a 


00 


«* 


•=*■ 


CO 


CO 


LO 


■tf 


r-. 


LO 


oo 


h* 


LO 


LO 


cn 


«* 


O 


CNI 


cn 


oo 


CTl 


OO 


CO 


LO 


, — 


uo 





*t 


CNJ 


< — ■ 











to 




cd 


It! 




r— 




LO 


«*■ 


CO 


CO 


* 


LO 


i — 


■=d- 


"*■ 


CO 


LD 


CO 


CO 


CT> 


CNJ 


cn 


CO 


LO 


LO 


00 


r- 


Cn 


«tf 


r^ 


00 


LO 


CI 


Lf) 


r-. 


LO 


Lf) 


Lf) 


LO 


r — 


CM 


i — 


OO 









rO 


ro 




o 




CT> 


t — 


co 


CNJ 


CO 


OO 


00 


LD 


co 


CO 


h». 


CO 


r — 


Lf) 


LO 


OO 


r-s 


LO 


r-s 


LD 


oo 


oo 


1 


o 


Lf) 


CO 


r-- 


■Sfr 


^— 


oo 


CO 


LO 


00 


CNJ 


cr> 


CTl 


P>- 


OO 




CD 







>> 

<d 
■a 






E 
re 

S- 

CJ3 





CO 


Ol 


LO 


«sr 


CNI 


r-» 


CO 


CO 


«tf 


Vo 


I — 



cn 



CO CO 

i — r~~. 

cn co 

CNI co 

o o 



w in n 





CO 




rrt 


_o 




LO 


CO 


cn 


<i" 


to 


! ' 


<cf 


cn 


00 


LO 


OO 


r~" 


o 


«fr 


o 


CNJ 


LO 


cn 


LO 


CO 


CJ 


«3" 


cn 


LO 


r^- 


<* 


LD 


m 


O 


Lf) 


LO 


«d- 


i — 


CNJ 





ro 




CO 


Id 




oi 




CD 


r-> 


rO 


CM 


r-« 


r-. 


Lf) 


LO 


LD 


Lf) 


LO 


r~- 


«=J- 


OO 


LO 


h-. 


CNJ 


Li) 


CO 


CM 


!■». 


O) 


«3" 


LD 


i — 


CNJ 


i — ' 


r-- 


r-- 


t^ 


( — 


00 





co 




ro 


(0 




co 


fO 


LO 


LD 


<d 


■• — 


CO 


CO 


CNI 


r-» 


r>- 


LO 


r _ 


o 


LO 


i — 


co 


<cf 


cn 


<!*• 


CO 


oo 


CO 


r-^ 


CO- 


-r 


r- 


LO 


o 


r-. 


o 


CO 


CNI 


LO 


LO 


CNJ 


■st 


CNI 


i — 











CO 


rrs 






CO 


CO 


CM 


CNJ 




113 


cn 


CO 


CO 


OO 




cn 


CJ 


CNJ 


CO 


LD 




Lf) 


LO 


CO 


r>- 


00 




cn 


O 


CO 


CO 


r-^ 




Lf) 


CO 


CD 


LO 


<* 




oo 


LO 


r— 


r— 


LO 




CO 


^™ 


LO 


CO 


OO 




o 




P-- 








r— 










>. 












CO 




















I — I 




V) 




1 — 1 


*—H 


Li_ 


X 


p= 




U- 


c*_ 


C3 


LL. 


to 


i — I 


o 


o 


z: 


Q 


s_ 


5*" 


"Z. 


CJ 


a 


s: 


CD 


o 



o 



X 

LL. 
Q 



I/) 
CD 
S- 

CC 

C5 

O" 
LO 



c0 
CD 



CD 
II jQ 

O L0 
CD 

• " CD 
SVr- 
+-> "O 
T- E 
i — 3 
•i — 
jQ II 

-M X 

t/) •i— 

CD 4- 
Cn d) 

■r- i.. 

-a o_ i 



x 



■ QJ 



•r- CD 
<+- r— O 
<+- JD K 
3 1- CD 
CO +-> 

(/> II 
Q CD 
cn X 

- « -f— *r— 

S- TJ 4- 
aj 4- 

+J II 3 
</) 
X 

X 
4- 
>, CD •" 
S- S- CD 

-a cl^h 

CO 

II Q+> 



-p 
ro 



Q 



CD 

T- 

5 

O 



O 

4_ 

CD 

+-> 

CD 
S_ 

CO 

co 

C 

o 

•T— 
+J 

CO 
•r - 

> 

a) 

5- 
jD 

CO 



CU II 
JD 

•r- X 

4- -r- 

4- 

4J 4- 

c rs 

CD <S) 
CD 
J- i— l 

a) 

CD LO 

■a cd 



s- 

CD 

+J 

4-} 
CD 



CO =3 
i- 1— 
+-> O 
Z3 CO 

a) 
c 

II CD 
CD 
i. 

CD 
4-> 

CD 

CD 1 — 
-M (0 

:rs 

CD 

E 1 — 



Q 



LO 

O 



V 



CNI 



*j — 
E II 
CO 
CD CO 

o 22: 



O 



Q_ 
CO 



131 



UJ 
Q. 
X 



< 

a 

LU 



a 

< 
>- 



o 



ai 
-a 



oe: 



CD 



Cn 

o 



O 
CO 



CM 











CO 








«4- 


CO 


LO 


CO 


LO 


en 


r— 


CO 


LO 


CXI 


LO 


CO 


00 


LD 


~- 


CM 


r" 


co 


o 


cn 


CTl 


C\J 



to cr> 











O 








CO 


CM 


CO 


CO 


CO 


■4- 


i — 


-r 


in 


I — 


«tf 


LO 


O 


CTl 


LD 


en 


CM 


CO 


«*■ 


cc 


CM 


CM 



CO 











co 










co 


CM 


"3" 


CT> 


*3" 


r-- 


CTi 


O 


CVi 


co 


«t 


«C* 


r^ 


LO 


00 


LO 


i — 


CD 


LO 


CO 


!■ ' 


CD 


r- 


r— 


CO 


CO 


LO 


CM 


r— 




; 











O 






-Q 


to 


CD 


CO 


r» 


' — 


CM 


CM 


«* 


^r 


CTl 


r*» 


CO 


LO 


Ol 


O 


CO 


i — 


LO 


CO 


CT> 


en 


en 


o 


CO 


01 


O 


CO 


: 


>* 


>* 


CM 





CO 



to 

LjJ 
CD 
I — i 
Q 

CC 

o 

LL. 



CO 

< 

I ! 

cc 



cc 



Li_ 
O 

LU 

o 

cc 

O 
CO 






Cm 











LO 


















CO 


co 












C_J 


CO 


LO 


r-» 


oo 










re 


LO 


a-, 


CXI 


CO 


ai 










co 


CO 


CO 


CO 


i— . 


o 


CO 


ro 


CO 


f« 


O 


CO 


en 


CO 


LO 


o 


r--. 


■— 


■=3- 


LO 


CXi 












Ol 


C-- 


eo 


<d- 


C\! 












co 


i — 


<t- 


CO 


o 












i — 


CD 


co 


o 


LO 












r-% 


j — 


ai 


CO 


CO 












t — ■ 


co 


. — 


LO 


CO 












LO 


CM 


j — 







o 

CO 

< — I 
CO 



CO 

LU 
CC 

=C 

co- 
co 



aj 

CD 
rC 
S_ 
o 
u. 











(0 


















re 


r-~ 












(0 


rc 


03 


CM 


^r 












>5f 


I-v 


CO 


CO 


LO 












LO 


P-. 


^f 


CO 


cr> 










«*■ 


CD 


CM 


c> 


<- 


r-s 


re 


re 


re 


ra 


LO 


O 


r^ 


LO 


f— 


<Sf 


o 


CTl 


CO 


CM 


CO 


O 


i — 


<* 


ai 


CO 


CM 


, 


en 





CO 


CVi 


co 


o 


CM 


r— 


r— 


r-». 


CO 


r-- 


iO 


CM 


LO 


CXI 


^r 




CTl 


CO 


«=t- 


CO 


CO 


<3" 


co 


CO 






i — 
O 
<* 
LO 


en 
r--. 

CO 


*3- 

LO 

to 

«3" 


OO 

I 

CO 





CO 



<4- 



co 

CO 



CO 



CXi 



s. 
aj 

•r— 

S- 

CO 



C 
<U 
CJ 
S- 

C1J 

a. 





a 




LL. 


co 


a 


LL_ 


> 


Q 


Q 


sc: 


CO 


CO 


s: 


SC 


o 


sr 


Q 


Q 


CO 



> 
re 

"O 



S- 

CD 



CO 

a 



o 

Q 



X 

a 









132 



OS 



UJ 

O 
OC 

o 

00 



T3 
CD 

c 

•i — 
+J 

e 
o 

C_3 



CO 
CO 



CO 



o> 

■D 

E 



a: 



CD 

oo 

CO 
SL 

o 



cd 



CD 
CD 
(O 
i. 

o 











00 




«* 




in 


CO 


Ol 


CM 


CM 


co 


o 


«*■ 


o 


CO 


i-» 


CO 


r>. 


CM 


CO 


o 


CM 


CO 


CM 


o 


o 


r— 











CTl 




en 




CD 


o 


Ci 


r-- 


CNJ 


r*-. 


CO 


vt- 


O 


h% 


co 


Ol 


00 


O 


o 


Ol 


I — 


co 


CO 


1 — 


«* 


r~. 



LO ^ r~ I— i— 





r~- 




r-- 


cn 


1 — ' 


-^r 


O 


CNI 


LO 


CO 


O-i 


CM 


U0 


o 


1--, 


i — 


o 


co 


o 


O 


>* 


CO 


CNJ 


co 


lo 


<^r 


«t 


CM 


LT> 


CNJ 


: — 

















JO 




n3 




(0 


«t 


(0 


■d- 


(C 


CO 


o 


r-. 


CTl 


CO 


CO 


l-» 


CO 


co 


CO 


«d- 


«* 


n— 


o 


r-^ 


^f- 


Ol 


r~. 


CD 


r*» 


■tf 


en 



CO CO r— CM CTl 
CO CO CO CO CM 
CO i — CO CO 





>> 




<w 




-a 




o 


M 


• CD 


(0 


r— -M 


•r— 


S 


S- 




O) 


CO 


+J 


£ 


•r- 


(O 


s~ 


<~ 


CJ> 


C£5 



o 



1 — i 


i — i 


u_ 


x 


u_ 


£££ 


O 


u_ 


Q 


o 


2^ 


_o, 


e: 


Q 


a 


21 



QJ 

II T~ 

s: co 

o CJ 

CD 
• « •[— 

+J e 
•r- rs 

•i- ii 

JO 

■r- X 

+-> -r- 
01 <•(- 
CU CD 
CD S- ■ 

•r- O- E 

XI o 

zd ■<- 

ii -p 

." CD 

X CD S- 

•i- i— o 

4- JO X 

<4- -r- CD 
=3 4-> 
CO C0 II 

CD 
O CD X 
■r— *r— 
•"T3 4- 
S~ 4- 

CD II 3 





+-> CO 




-M X 




<0 -r- X 




£ 4- 




<D •« 




>, S- CD 




S- Q-^i 




T3 fO 




Q +-> 




11 E 




, r. -r- 




s: s- 




Q CD II 




JO 




-r- X 




• • q- -i- 




CD 4- 




E +J 4- 




•r- C 3 




2 CD co 




O CD 




r— S- i-h 




r— CD 




o +■* •« 




4- 0) co 




-a cd 




CD i— 




£i — JD 




+-> (0 =5 




S- r— 




CD 4-> O 




!- 3 ui 




(0 CD 




C +-> 




E E 




O II CD 




•i- CD 




+-> u_ s_ 




(SQ QJ 




•i- ■Z. 4J 




> CD 




cd •« , a 




S- S- 


t 


jo coi — 


00 


JCX +J rO 


CD 


as +-> S- 


S^ 


rc J-> 


fO 


■—• £ o 


ZS 


CO CD 


CT 


CJ E i — UO 


00 


S-. -r- O O 




CD E II 


C 


-P (C 


rC 


+J enco v v 


CD 


o s-o 


s: 


_J O ^ O- Q_ 




CM fQ J2 






133 



LU 



az 

LlJ 
D. 
X 



oo 
o 



OO 
1 — I 
D£ 
LU 

h- 

c£ 
ce 
<C 

re 

CJ 

oo 
oo 

< 
o 

cc 

<c 
o 



LU 
CO 

u_ 

o 

LU 

o 

< 
i — i 
or: 

> 

U_ 

O 

I — ) 

oo 
>- 

_J 

<C 

< 
oo 

LU 
Q£ 

<C 

ro 
err 

oo 



CO 

< 

LU 






LU 



cn 













CM 










CO 




CM 


o 


ro 


lf> 


s- 




CO 


CO 


o 


O 






; 


CO 


CO 


LO 


OO 


o 


CO 


LO 


O! 




o 


r*. 


CM 


OO 


co 


CM 


: 


LO 


CM 


! ' 


r- 


ro 


o 


CO 


-a 




o 


CM 


CM 


cn 


1 — 


LO 


O 


CO 


CO 


r-» 


o 


r** 


LO 


r-. 


sr 


o 


CD 


CO 


o 


<m 


00 


i — 


OO 


LO 


oo 


CM 


CO 


CO 


CO 


io 


•r— 


oo 


>5f 


CM 


On 


LO 


o 


oo 


«tf 


to 


■=f- 


i — 


00 


cn 


r». 


, — 


rd 

E 




CO 


OO 


CO 


LO 


CO 


CD 


LD 


o 


: 


«fr 


LO 


r~ 


LO 


LO 




o 


on 


co 




CO 


CM 


LO 


o 


CXI 


«* 




, 


, . 




OS 




■sf 


Cvi 


ro 




t — 


r"~" 




I — 















CU 



CU 

cn 
ro 
S- 
O 



IX 



LU 
CJ 
DC 

ro 
O 

CO 



a; 

Cn 



<U 
■cn 
ro 
S. 

o 



CM 
f0 

SL 
CJ 

+-> 

'I — ■ 

s_ 
o 





























DO 








^r 










«*■ 




■=3- 


^— 


■=Th 


r-» 


CJ 


o 


o 


co 






r— 


r» 


cn 


l — 


«=r 


CO 


«sf 


CM 


to 


«5T 


CO 


CO 


h~- 


oo 


r-. 


r^ 


. — 


CO 


00 


on 


"=f 


O 


CJ 


cn 


cd 


O0 


LO 


CM 


r-. 


CO 


r-. 


CD 


CO 


O 


CTl 


CO 


LO 


CO 


on 


CO 


r^ 


LC) 


on 


CO 


oo 


vo 


on 


CO 


i — 


oo 


P-« 


O 


OJ 


«tf 


LO 


OO 


co 


CO 


LO 


cn 


CO 


CM 


i — 


CO 


~ 


r». 


CO 


o 


CM 


oo 


~ 


o 


^t 


CD 


VO 


o 


co 


<=3- 



CM OO 



C\J 





























JO 








r0 










-Q 




ra 


ro JO. 


co 


n3 


rd 


rC 


r~. 






ra 


ra 


r— 




o 


«d- 


oo 


p-. 


"3- 


CO 


CM 


CD 


r0 


ro 


I — > 


r— 


CO 


oo 


CO 


r™ 


oo 


CXI 


C-J 


t»s. 


«* 


CD 


i — 


CSJ 


o 


oo 


OO 


CO 


CO 


cn 


oo 


LO 


Ol 


CO 


cn 


CO 


co 


oo 


CO 


r->- 


CO 


CO 


**■ 


CO 


rn 


LO 


CO 


CO 


p^. 


i — 


on 


CO 


r^ 


r-. 


CM 


cn 


LO 


CO 


LO 


LO 


LO 


CO 


Ol 


Cv! 


CM 


r-» 


CJ 


o 


LO 


CO 


oo 


o 


CO 


■st 


CD 


«* 


CO 


o 


CO 


00 


CO 


CM 


r-*. 


«d- 


co 


CM 


«tf 


on 


CsJ 


=^ 


o 


r-. 


=d- 


r-. 


oo 


LO 


!■•« 


oo 


CM 


on 


r». 





cn 


LO 


! 




O 


on 


^r 


[*■* 




1 — 










r-~ 


«d- 


r«. 




CM 


! — 

























ra 














r0 




r0 


CO 


ro 


ra 


r0 


Ol 






ro 


rO 


co 


rO 


^~ 


00 


TT 


r~- 


CO 


o 


CO 


LO 


rO 


r0 


on 


CM 


CM 


on 


CM 


r>. 


^1- 


r~^ 


*r 


O 


o 


r — 


CO 


r-. 


LO 


on 


O 


CD 


r^- 


r-v 


«* 


r^ 


CM 


oo 


O 


J — 


o 


CT-: 


LO 


*S- 


CO 


TT 


CM 


co 


C7! 


CO 


CO 


on 


Cn 


LO 


r-. 


«^r 


i — ■ 


r^. 


CO 


UO 


oo 


CM 


CO 


CM 


a; 


CM 


r*» 


"* 


O 


«* 


CM 


«* 


a) 


LO 


o 


CM 


o 


CM 


>5fr 


LO 


t 


CM 


CM 


co 


r--. 


uo 


r*. 


O 


cn 


CD 


LO 


>— 


CM 


O0 


^r- 


OO 


CO 


co 


c^ 


on 


Ti- 


OO 


TT 


OO 


cn 


LO 


■=d- 


o 


CO 


J — 1 


; 


i — 


■=s- 


CO 




<^- 






, — 




— 


CO 


CO 




CM 


CM 



















"O 



6-S 



CO 





3C 


SB 


3: 


ca 


h- 


CQ 


X 


CD 


LU 


oo 


CO 



o 

i— 
o 



CJ 



rr 




<r 


LU 










< 


r- 


LU 


>- 








LU 


LU 


< 


OS 


LU 


•— 






t~\ 


_J 


Lu 


< 




<r 




- — ^ 


<r 








OS 


LJ_ 




?fS, 


rf 


OO 


CO 


LU 


LU 


+ 


^ H 


**_-* 


CO 


oo 


00 


>- 


s* 


>- 


s^ 






cC 


<? 


LU 


o 


LU 


-— ^ 


CO 


c^ 


o 


CJ) 


1 




2 




i 


—J 


oc 


CrC 


CQ 


!— 


CJ 


CO 


LU 


LjJ 


<r 


<r 


i — i 


<■ 


h — ! 


LU 


I — I 


: — i 


c_> 


o 


C£ 


Lu 


S«i 


I 


>- 


>- 



CU 

S- 
rc 
3 
CT 



X3 


to 


E 


e 


r0 


rd 




S_ 


4-> 


on 


o 


o 


jc- 


1 — 




•: — 


ii 


J^ 


~s 


tz 


C_J 


': — 


re 




CO 


1 




i 


-a 


re 


E 




ro 


• « 



CD cn 

I— T- 

o ai 
re s 

>1 O 
r— CO 
CU i- 
> +J 

+-> CU 
O > 

a> -r- 

CL4-> 

co co 
OJ CU 

5- cn 

"TO- 
CO 
4- 1 >, 

^r: 4-> 
cn o_ 

•r- E 

cu cu 
3: 
II 

-a 3 

o I— 
JO CD 

a 
^. 

c: -o 
rs c 
s- ro 

CO •« 

>) 

■a i— 
sc cu 

ro > 

1 — +-> 
i— u 

rs cu 

4- CO- 
CO 

- cu 

4-' 

a. - 

& +J 
CU J= 

DO 
II -r- 

CU 

CO 

re co 

OO l/) 

ro 

■a cj 

!= S- 

ra ro 

O 

cn -a 

Ll_ cu 



ro 3 •.- 

cu ca jc 

£ cu o 

- CM 



134 



TABLE 35. INDIVIDUAL 


DATA ON 


NUTRIENT 


DIGESTIBJ 


LITY ANE 


) VOLUNTARY INTAKE. 


EXPERIMENT 


I 
















Sheep 






Criteria 






Trial (Age) Forage 














NO. 4 


DMD 


NDFD 


DMI 


OMI 


NDFI 


FBW 


I (10) LQB 


174 


34.65 


32.51 


1049 


1006 


834 


34.5 




176 


40.97 


39.68 


1058 


1014 


840 


33.1 




183 


36.88 


36.01 


1247 


1196 


989 


35.8 




184 


36.22 


34.79 


1304 


1250 


1036 


37.6 




188 


34.34 


34.16 


1052 


1009 


833 


34.5 




190 


35.17 


35.47 


1015 


1008 


836 


32.2 




191 


35.55 


34.36 


1118 


1072 


886 


34.0 




198 


37.22 


34.83 


1246 


1195 


989 


34.9 


HQB 


177 


56.45 


49.81 


1342 


1249 


855 


36.3 




180 


54.39 


47.70 


1569 


1460 


1000 


38.1 




186 


57.16 


53.00 


1488 


1384 


950 


35.8 




192 


55.09 


49.57 


1595 


1485 


1014 


41.7 




195 


56.04 


49.91 


1530 


1423 


974 


39.9 




196 


55.09 


51.37 


1424 


1326 


909 


36.3 




197 


54.75 


48.60 


1429 


1330 


911 


37.6 




°199 


53.11 


44.13 


1574 


1465 


1003 


36.3 


ALF 


171 


54.5? 


42.93 


1423 


1269 


690 


34.9 




172 


49.78 


39.05 


1511 


1345 


731 


32.6 




173 


52.74 


37.84 


1873 


1668 


904 


38.1 




181 


52.27 


39.27 


1965 


1750 


949 


39.5 




185 


54.77 


44.26 


2158 


1922 


1042 


38.5 




189 


51.84 


40.33 


1854 


1651 


895 


37.2 




193 


54.86 


46.57 


1375 


1225 


665 


33.5 




200 


53.99 


42.33 


1943 


1731 


937 


38.5 


II (16) LQB 


174 


40.13 


40.26 


1273 


1213 


1002 


45.8 




176 


39.98 


40.31 


1312 


1251 


1035 


43.5 




183 


41.56 


41.97 


1482 


1413 


1166 


48.9 




184 


40.33 


40.20 


1487 


1418 


1173 


48.5 




188 


39.19 


38.89 


1197 


1141 


945 


42.2 




190 


41.51 


42.18 


1208 


1152 


951 


43.1 




191 


44.96 


47.99 


912 


870 


719 


37.2 




198 


41.17 


41.59 


1447 


1380 


1140 


43.5 



Table 35 - Continued 



135 



2 3 
Trial (Age) Forage 


Sheep 

No. 4 






Crite 


. 1 

na 






DMD 


NDFD 


DMI 


OMI ' 


NDFI 


FEW 


II (16) HQB 


177 


56.76 


54.65 


1914 


1774 


1249 


52.6 




180 


52.72 


49.29 


1794 


1663 


1171 


50.3 




186 


56.21 


52.87 


1928 


1787 


1257 


48.1 




192 


56.48 


53.21 


1945 


1803 


1270 


57.6 




195 


57.82 


57.05 


1564 


1450 


1023 


45.3 




196 


56.83 


54.69 


2030 


1881 


1325 


51.7 




197 


57.15 


55.92 


1848 


1713 


1205 


51.2 




199 


57.72 


55.48 


1951 


1808 


1272 


46.7 


ALF 


171 


56.31 


47.44 


2222 


1961 


1071 


53.1 




172 


54.62 


46.83 


2203 


1945 


1065 


47.2 




173 


54.58 


46.91 


2064 


1822 


998 


49.9 




181 


53.30 


45.24 


2155 


1902 


1043 


53.9 




185 


53.01 


45.46 


2534 


2236 


1227 


54.9 




189 


52.58 


44.33 


2252 


1986 


1088 


47.2 




193 


56.18 


48.67 


1873 


1653 


908 


45.8 




200 


53.81 


43.54 


2254 


1990 


1082 


50.8 


III (22) LQB 


174 


41.18 


40.58 


1318 


1258 


1022 


46.3 




176 


40.55 


40.54 


1252 


1195 


968 


42.2 




183 


43.81 


44.71 


1404 


1339 


1088 


47.6 




184 


44.75 


46.11 


1531 


1461 


1182 


50,3 




188 


40.76 


42.08 


1451 


1384 


1123 


40.8 




190 


43.31 


45.11 


1872 


1786 


1452 


61.7 




191 


43.38 


44.83 


1317 


1257 


1021 


46.7 




198 


42.82 


43.13 


1499 


1431 


1163 


44.4 


HQB 


177 


58.82 


58.06 


2273 


2108 


1445 


57.1 




180 


58.80 


57.83 


2130 


1975 


1353 


54.9 




186 


57.63 


55.24 


2239 


2076 


1408 


53.5 




192 


60.51 


58.55 


2387 


2213 


1506 


61.2 




195 


58.02 


55.68 


1625 


1506 


1023 


54.4 


■• 


196 


60.08 


58.21 


2060 


1910 


1307 


58.5 




197 


60.34 


58.43 


2127 


1972 


1349 


58.1 




199 


56.81 


54.38 


2165 


2008 


1366 


48.5 









136 



Table 35 - Continued 





2 3 
Trial (Age) Forage 


Sheep 
No. 4 






Crite 


ria' 






DMD 


NDFD 


DM I 


OMI 


NDFI 


FBW 


III (22) ALF 


171 


58.34 


54.56 


2602 


2309 


1260 


59.42 




172 


55.21 


49.38 


2712 


2408 


1316 


45.81 




173 


57.88 


53.44 


2735 


2427 


1325 


53.07 




181 


59.01 


54.78 


2877 


2553 


1396 


59.87 




185 


55.14 


51.10 


2877 


2554 


1394 


57.15 




189 


57.48 


51.98 


2740 


2432 


1330 


53.07 




193 


58.63 


52.91 


2401 


2132 


1165 


52.16 




200 


56.74 


50.68 


2665 


2367 


1291 


54.88 


IV (28) LQB 


174 


38.82 


38.83 


1348 


1287 


1061 


49.4 




176 


37.84 


36.89 


1590 


1518 


1251 


47.6 




183 


39.19 


39.18 


1736 


1657 


1369 


54.4 




184 


39.91 


41.98 


1644 


1569 


1295 


53.9 




188 


41.89 


41.78 


1461 


1393 


1151 


44.9 




190 


41.36 


40.51 


1890 


1804 


1489 


65.3 




191 


39.53 


40.32 


1240 


1183 


975 


48.9 




198 


39.17 


39.99 


1545 


1474 


1216 


46.7 


HQB 


177 


55.64 


52.34 


2532 


2343 


1612 


61.2 




180 


53.27 


49.86 


2306 


2133 


1465 


59.4 




186 


54.54 


53.18 


2638 


2440 


1680 


59.9 




192 


52.32 


50.76 


2689 


2488 


1714 


67.6 




195 


57.35 


59.33 


1602 


1482 


1016 


49.9 




196 


51.60 


51.45 


2182 


2018 


1389 


64.9 




197 


52.70 


49.81 


2271 


2101 


1449 


63.0 




199 


53.06 


50.51 


2404 


2224 


1535 


55.3 


ALF 


171 


53.32 


46.75 


2772 


2460 


1323 


63.9 




172 


49.39 


39.51 


2818 


2501 


1352 


55.8 




173 


49.27 


39.60 


3136 


2783 


1496 


58.5 




181 


52.74 


43.60 


3298 


2927 


1584 


63.9 




185 


53.24 


43.93 


3116 


2755 


1494 


61.7 




189 


48.45 


38.19 


3035 


2694 


1457 


60.3 




193 


50.55 


41.52 


2651 


2353 


1267 


58.1 




200 


57.07 


48.93 


2908 


2581 


1393 


58.5 



Letter(s) abbreviations are the following: DM = dry matter; D suffix 
digestibility {%); NDF = neutral detergent fiber; I suffix = intake 
(grams/day); OM = organic matter; FBW = full body weight (kg). 

2 
Animal age in months. 

3 
See table 2 for description of forages. 

4 
Ear tag number. 






137 



TABLE 


36. INDIVIDUAL DATA 


ON NUTRIEN1 


' DIGESTIBILITY 


AND VOLUNTARY INTAKE. 




EXPERIMENT II 














Age 2 


c 3 
Forage 


4 
Sheep No. 






Criteria 






DMD 


NDFD 


DMI 


OMI 


NDFI 


FBW 


12 


LQB2 


19 


30.07 


28.53 


939 


905 


744 


28.7 






51 


32.68 


30.30 


887 


855 


693 


40.1 






41 


31.51 


29.71 


1307 


1260 


1025 


41.7 






44 


37.68 


38.12 


819 


789 


643 


40.7 






52 


29.20 


27.51 


1158 


1117 


909 


47.1 






49 


35.07 


33.7 


960 


926 


753 


48.0 


24 


LQB2 


8 


39.17 


40.28 


803 


774 


635 


31.4 






12 


32.35 


30.88 


1028 


991 


807 


36.1 






27 


34.38 


33.09 


1326 


1279 


1037 


42.2 






17 


35.19 


34.54 


1178 


1135 


921 


45.5 






31 


32.77 


30.27 


1400 


1350 


1098 


46.5 






3 


33.70 


32.47 


1290 


1243 


1013 


50.0 


36 


LQB2 


180 


32.38 


31.78 


1239 


1195 


974 


50.8 






199 


33.84 


31.94 


1352 


1304 


1064 


50.5 






171 


30.26 


27.99 


1375 


1325 


1077 


57.4 






173 


34.27 


32.66 


1370 


1321 


1075 


52.6 






185 


37.60 


36.67 


1139 


1097 


895 


57.5 






196 


32.09 


30.01 


1239 


1194 


971 


59.7 


12 


HQB2 


4 


55.22 


54.20 


1452 


1347 


898 


33.8 






47 


55.03 


52.81 


1803 


1672 


1106 


47.8 






43 


57.42 


55.60 


1815 


1684 


1116 


49.3 






45 


53.66 


50.97 


2119 


1967 


1304 


50.5 






48 


54.86 


52.01 


2279 


2115 


1403. 


58.6 






50 


55.16 


53.18 


1917 


1779 


1181 


51.7 


24 


HQB2 


23 


55.22 


54.81 


1333 


1236 


820 


37.7 






28 


53.59 


51.27 


1799 


1670 


1107 


43.5 






2 


55.35 


53.08 


2228 


2067 


1371 


47.5 






18 


54.64 


51.71 


1851 


1716 


1136 


48.1 






14 


50.73 


46.50 


2630 


2440 


1618 


56.4 






20 


53.60 


48.93 


1901 


1764 


1167 


50.9 






138 



Table 36 - Continued 



2 
Age^ 


Forage 


4 
Sheep No. 






Cri 


tena 






DMD 


NDFD 


DMI 


OMI 


NDFI 


FBW 


36 


HQB2 


184 


55.68 


54.60 


2407 


2234 


1488 


56.2 






200 


53.44 


53.16 


2389 


2216 


1466 


59.2 






189 


52.68 


48.34 


2724 


2529 


1678 


64.1 






193 


54.40 


52.39 


2343 


2174 


1446 


61.1 






192 


53.38 


50.86 


2504 


2323 


1547 


70.0 






197 


54.34 


51.91 


2485 


2306 


1528 


66.5 



Letter(s) abbreviations are the following: DM = dry matter; D suffix 
digestibility (%); NDF = neutral detergent fiber; I suffix = intake 
(grams/day); OM = organic matter; FBW = full body weight (kg). 

Animal age in months. 
3 
See table 11 for description of forages. 

Ear tag number. 



LITERATURE CITED 



Alexander, G. and 0. B. Williams. 1973. The Pastoral 

Industries of Australia. Practice and Technology 
of Sheep and Cattle Production. Sydney University 
Press. 

Allden, W. G. and R. Scott Young. 1964. The summer 

nutrition of weaner sheep: herbage intake follow- 
ing periods of differential nutrition. Aust. J. 
Agr. Res. 15:989. 

Anand, B. K. 1961. Nervous regulation of food intake. 
Physiol. Rev. 41:677. 

Anand, B. K. and J. R. Brobeck. 1951. Hypothalamic con- 
trol of food intake in rats and cats. Yale J. 
Biol. Med. 24:123. 

Andersson, B. and B. Larsson. 1961. Influence of local 
temperature changes in the preoptic area and 
rostral hypothalamus on the regulation of food 
and water intake. Acta Physiol. Scand. 52:75. 

Andrews, R. P., M. Kay and E. R. Orskov. 1969. The 

effect of different dietary energy concentrations 

on the voluntary intake and growth of intensively 
fed lambs. Anim. Prod. 11:173. 

Andrews, R. P. and E. R. Orskov. 1970. A note on the 
effect of bulk density and digestibility on the 
voluntary intake of concentrate diets by sheep of 
two ages. Anim. Prod. 12:335. 

A.O.A.C. 1965. Official Methods of Analysis (10th ed.). 
Association of Official Agricultural Chemists. 
Washington, D. C. 

Arnold, G. W. 1970. Regulation of food intake in grazing 
ruminants. In: A. T. Phillipson (Ed.) Physiology 
of Digestion and Metabolism in the Ruminant. Oriel 
Press Limited, Newcastle upon Tyne, England. 

Baile, C. F. 1968. Regulation of feed intake in ruminants 
Fed. Proc. Fed. Amer. Soc. Exo. Biol. 27:1361. 



139 






140 



Baile, C. A. 1969. Propionate as a possible feedback for 
the control of meal size. Fed. Proc. 28:491. 

Baile, C. A. 1971. Control of feed intake and the fat 
depots. J. Dairy Sci. 54:564. 

Baile, C. A. and A. W. Mahoney. 1967. Hypothalamic func- 
tion in ruminant food intake regulation. In: Regu- 
lation of Hunger and Satiety. Proc. Seventh Intern. 
Congr. Nutr. 2:67. 

Baile, C. A., A. W. Mahoney and J. Mayer. 1967a. Place- 
ment of electrodes in the hypothalamus of goats. 
J. Dairy Sci . 50:756. 

Baile, C. A., A. W. Mahoney and J. Mayer. 1967b. Pre- 
liminary report on hypothalamic hyperphagia in rumi- 
nants. J. Dairy Sci. 50:1851. 

Baile, C. A., A. W. Mahoney and J. Mayer. 1967c. Pre- 
liminary report on feeding activity and hypothalamic 
temperature in goats. J. Dairy Sci. 50:1854. 

Baile, C. A., A. W. Mahoney and J. Mayer. 1968. Induction 
of hypothalamic aphagia and adipsia in goats. J. 
Dairy Sci . 51 : 1 474. 

Baile, C. A. and F. H. Martin. 1971. Hormones and amino 
aicds as possible factors in the control of hunger 
and satiety in sheep. J. Dairy Sci. 54:897. 

Baile, C. A. and F. H. Martin. 1974. Parotid secretion 

and feeding in sheep following intraventricular in- 
jection of L-norepi nephri ne, dL- i soproterenol , pento- 
barbital, and carbachol . J. Dairy Sci. 57:308. 

Baile, C. A., F. H. Martin, J. M. Forbes, R. L. Webb and 
W. Kingsbury. 1974. Intrahypothal amic injections 
of prostaglandins and prostaglandin antagonists and 
feeding in sheep. J. Dairy Sci. 57:81. 

Baile, C. A. and J. Mayer. 1967. Intragastric injections 
of liquid diet, water, and acetate and meal patterns 
of goats. Amer. J. Physiol. 213:387. 

Baile, C. A. and J. Mayer. 1968a. Hypothalamic temperature 
and the regulation of feed intake in goats. Amer. 
J. Physiol. 214:677. 






141 



Baile, C. A. and J. Mayer. 1968b. Effect of intravenous 
vs. intraruminal injections of acetate on feed in- 
take of goats. J. Dairy Sci. 51:1490. 

Baile, C. A. and J. Mayer. 1968c. Effects of insulin 
induced hypoglycemia and hypoacetoemi a on eating 
behavior in goats. J. Dairy Sci. 51:1495. 

Baile, C. A. and J. Mayer. 1969. Depression of feed in- 
take of goats by metabolites injected during meals. 
Amer. J. Physiol. 217:1830. 

Baile, C. A. and J. Mayer. 1970. Hypothalamic centres: 

Feedbacks and receptor sites in the short-term con- 
trol of feed intake. In: A. T. Phillipson (Ed.) 
Physiology of Digestion and Metabolism in the Rumi- 
nant. Oriel Press Limited, Newcastle upon Tyne, 
Engl and . 

Baile, C. A. and C. McLaughlin. 1970. Feed intake of 

goats during volatile fatty acid injections into 4 
gastric areas. J. Dairy Sci. 53:801. 

Baile, C. A. and W. H. Pfander. 1966. A possible chemo- 

sensitive regulatory mechanism of ovine feed intake. 
Amer. J. Physiol. 210:1243. 

Baile, C. A. and W. H. Pfander. 1967. Ration density as 
a factor controlling food intake in ruminants. J. 
Dairy Sci. 50:77. 

Baile, C. A., C. W. Simpson, S. M. Bean, C. L. McLaughlin 
and H. L. Jacobs. 1973. Prostaglandins and food 
intake of rats: a component of energy balance regu- 
lation? Physiol. Behav. 10:1077. 

Bailey, R. W. and D. I. H. Jones. 1971. Studies on the 

hydrolysis by carbohydrases of plant cell-wall con- 
stituents in relation to pasture quality. Proc. 
New Zealand Soc. Anim. Prod. 31:82. 

Baker, R. D. 1964. Grassland recording. III. A reap- 
praisal of the use of livestock and starch-equivalent 
standards in assessing the utilized production from 
grassland. J. Brit. Grassld. Soc. 19:149. 

Balch, C. C. and R. C. Campling. 1962. Regulation of 

voluntary food intake in ruminants. Nutr. Abstr. 
and Rev. 32:669. 






142 



Barnes, R. F. 1973. Laboratory methods of evaluating feed- 
ing value of herbage. In: G. W. Butler and R. W. 
Bailey (Eds.) Chemistry and Biochemistry of Herbage. 
Vol. 3, p. 179-214. Academic Press. New York. 

Baumgardt, B. R. 1970. Control of feed intake in the 

regulation of energy balance. In: A. T. Phillipson 
(Ed.) Physiology of Digestion and Metabolism in the 
Ruminant. Oriel Press Limited. Newcastle upon Tyne, 
Engl and . 

Baumgardt, B. R. and A. D. Peterson. 1971. Regulation of 
food intake in ruminants. 8. Caloric density of 
diets for young growing lambs. J. Dairy Sci. 54: 
1191 . 

Bell, F. R. 1961. In: D. Lewis (Ed.) Digestive Physiology 
and Nutrition of the Ruminant. p. 59-67. Butter- 
worths, London. 

Bergstrom, S., L. A. Carlson and J. K. Weeks. 1968. The 
prostaglandins: A family of biologically active 
1 ipids . Pharm. Rev. 20:1. 

Bhattacharya, A. N. and R. G. Warner. 1968. Influence of 
varying rumen temperature on central cooling or 
warming and on regulation of voluntary feed intake 
in dairy cattle. J. Dairy Sci. 51:1481. 

Bines, J. A. 1971. Metabolic and physical control of food 
intake in ruminants. Proc. Nutr. Soc. 30:116. 

Bines, J. A., S. Suzuki and C. C. Balch. 1969. The quan- 
titative significance of long-term regulation of 
food intake in the cow. Brit. J. Nutr. 23:695. 

Blaxter, K. L. 1962. The Energy Metabolism of Ruminants. 
p. 99-100. Charles C. Thomas. Publisher. Spring- 
f i el d , Illinois. 

Blaxter, K. L. 1965. Energy Metabolism. Academic Press, 
New York, N. Y. / 

Blaxter, K. L., J. L. Clapperton and F, W. Wainman. 1966. 
Utilization of the energy and protein of the same 
diet by cattle of different ages. J. Agr. Sci. 67: 
67 . 

■Blaxter, K. L. and F. W. Wainman. 1961. Environmental 

temperature and the energy metabolism and heat emis- 
sion of steers. J. Agri. Sci. 56:81. 






143 



Blaxter, K. L. and F. W. Wainman. 1964. The utilization 

of the energy of different rations by sheep and 

cattle for maintenance and for fattening. J. Agri . 
Sci . 63 : 113. 

Blaxter, K. L. 5 F. W. Wainman and R. S. Wilson. 1961. 

The regulation of food intake by sheep. Anim. Prod. 
3:51. 

Blaxter, K. L. and R. S. Wilson. 1962. The voluntary in- 
take of roughages by steers. Anim. Prod. 4:351. 

Block, R. J. and D. Boiling. "1951. The Amino Acid Compo- 
sition of Proteins and Foods. Analytical Methods 
and Results. Charles C. Thomas. Springfield, 
Illinois, U.S.A. 

Bloss, R. E., J. I. Northam, L. W. Smith and R. G. Zimbelman. 
1966. Effects of oral melengestrol acetate on the 
performance of feedlot cattle. J. Anim. Sci. 25: 
1048. 

Bohman, V. 1955. Compensatory growth of beef cattle: The 
effect of hay maturity. J. Anim. Sci. 14:249. 

Boling, J. A., E. C. Falting, W. G. Hoekstra and E. R. 

Hauser. 1967. Feed intake of cattle in response to 
dietary dilution with polyethylene. J. Anim. Sci. 
26:1385. 

Boling, J. A., T. Kowalczyk and E. R. Hauser. 1969. Short- 
term voluntary feed intake and rumen volatile fatty 
acids of steers fed diets diluted with polyethylene 
particles. J. Anim. Sci. 28:84. 

Brobeck, J. R. 1948. Feed intake as a mechanism of temper- 
ature regulation. Yale J. Biol. Med. 20:545. 

Brobeck, J. R. 1960. Food and temperature. Recent Progr. 
Hormone Res. 16:439. 

Brody, S. 1945. Bi oenergeti cs and Growth. Reinhold Pub- 
lishing Corporation, New York. 

Brody, S. and R. C. Procter. 1932. Growth and development 
with special reference to domestic animals. Further 
investigations of surface area in energy metabolism. 
Missouri Agr. Exp. Sta. Res. Bull. 116. 






144 



Campling, R. C. 1966. A preliminary study of the effect of 
pregnancy and of lactation on the voluntary intake 
of food by cows. Brit. J. Nutr. 20:25. 

Campling, R. C. 1970. Physical regulation of voluntary 

intake. In: A. T. Phillipson (Ed.). Physiology of 
Digestion and Metabolism in the Ruminant. p. 226. 
Oriel Press, Newcastle upon Tyne, England. 

Campling, R. C. and C. C. Balch. 1961. Factors affecting 
the voluntary intake of food by cows. 1. Prelimi- 
nary observations on the effect, on the voluntary 
intake of hay, of changes in the amount of the reti- 
culo-ruminal contents. Brit. J. Nutr. 15:523. 

Campling, R. C. and M. Freer. 1966. Factors affecting 

the voluntary intake of food by cows. 8. Experi- 
ments with ground, pelleted roughages. Brit. J. 
Nutr. 20:229. 

Campling, R. C, M Freer and C. C. Balch. 1961. Factors 
affecting the voluntary intake of food by cows. 2. 
The relationship between the voluntary intake of 
roughages, the amount of digestion in the reticulo- 
rumen and the rate of disappearance from the diges- 
tive tract. Brit. J. Nutr. 15:531. 

Campling, R. C, M. Freer and C. C. Balch. 1962. Factors 
affecting the voluntary intake of food by cows. 3. 
The effect of urea on the voluntary intake of oat 
straw. Brit. J. Nutr. 16:115. 

Campling, R. C, M. Freer and C. C. Balch. 1963. Factors 
affecting the voluntary intake of food by cows. 6. 
A preliminary experiment with ground, pelleted hay. 
Brit. J. Nutr. 17:263. 

Carr, S. B. and D. R. Jacobson. 1967. Intraruminal addi- 
tion of mass or removal of rumen contents on volun- 
tary intake of the bovine. J. Dairy Sci. 50:1814. 

Chicco, C. F., C. B. Ammerrnan and P. E. Loggins. 1973. 
Effect of age and dietary magnesium on voluntary 
feed intake and plasma magnesium in ruminants. J. 
Dairy Sci . 56:822. 

Church, D. C. 1971. Digestive Physiology and Nutrition of 
Ruminants. Vol. 2 - Nutrition. Chapter 27. Oregon 
State University, Corvallis, Oregon. 



145 



Colburn, M. W. and J. L. Evans. 1958. Reference base, W , 
of growing steers determined by relating forage in- 
take to body weight. J. Dairy Sci. 51:1073. 

Comline, R. S. and D. A. Titchen. 1961. In D. Lewis (Ed.) 
Digestive Physiology and Nutrition of the Ruminant. 
p. 10-22. Butterworths , London. 

Conrad, H. R. and J. W. Hibbs. 1969. Body size, digesti- 
6 bility, and forage intake. Invitational paper 

presented at the Amer. Soc. Anim. Sci. Ann. Meeting, 
Purdue University, Lafayette, Indiana. 

Conrad, H. R. , A. D. Pratt and J. W. Hibbs. 1964. Regula- 
/tion of feed intake in dairy cows. I. Change in 
importance of physical and physiological factors 
with increasing digestibility. J. Dairy Sci. 47: 
54. 

Cook, C. W.. , J. E. Mattox and L. E. Harris. 1961. Compara- 
tive daily consumption and digestibility of summer 
range forage by wet arid dry ewes. J. Anim. Sci. 
20:866. 

Coop, I. E. and K. R. Drew. 1963. Maintenance and lacta- 
tion requirements of grazing sheep. Proc. New Zea- 
land Soc. Anim. Prod. 23:53. 

Corbett, J. L. 1960. Faecal-index techniques for estimat- 
ing herbage consumption by grazing animals. Proc. 
VHIth Int. Grassl. Congr. p. 438. 

Corbett, J. L. 1968. Variation in the yield and composi- 
tion of milk of grazing Merino ewes. Aust. J. 
Agric. Res. 19:283. 

Corbett, J. L., J. P. Langlands and G. W. Reid. 1963. 
Effects of season of growth and digestibility of 
herbage on intake by grazing dairy cows. Anim. 
Prod. 5:119. 

Crampton, W. E., E. Donefer and L. E. Loyd. 1960. A nutri- 
tive value index for forages. J. Anim. Sci. 19:538. 

Crichton, J. A., J. N. Aitken, A. W. Boyne. 1959. The 

effect of plane of' nutrition during rearing on 

growth, production, reproduction and health of dairy 
cattle. Anim. Prod. 1:145. 



146 



Curran, M. K. and W. Holmes. 1970. Prediction of the 

voluntary intake of food by dairy cows. 2. Lacta- 
ting grazing cows. Anim. Prod. 12:213. 

Curran, M. K. , R. H. Wimble and W. Holmes. 1970. Pre- 
diction of the voluntary intake of food by dairy 

cows. 1. Stall-fed cows in late pregnancy and 
early lactation. Anim. Prod. 12:195. 



Davey, R. J. and G. H. Wellington. 1959. 
use of hormones in lamb feeding. I 
performance. J. Anim. Sci. 18:64. 



Studies on the 
Producti on 



Davis, J. D. , R. 0. Gallagher, R. F. Ladove and A. J. 

Turavski. 1969. Inhibition of food intake by a 
humoral factor. J. Comp. Physiol. Psychol. 64:407. 

Davis, S. L., U. S. Garrigus and F. C. Hinds. 1970a. 

Metabolic effects of growth hormone and diethylstil- 
bestrol in lambs. II. Effects of daily ovine growth 
hormone injections on plasma metabolites and nitro- 
gen retention in fed lambs. J. Anim. Sci. 30:236. 

Davis, S. L., U. S. Garrigus and F. C. Hinds. 1970b. 

Metabolic effects of growth hormone and diethylstil- 
bestrol in lambs. III. Metabolic effects of DES. 
J. Anim. Sci. 30:241. 



Dewar, A. D. 1962. The nature 
by progesterone in mice. 
67:112. 



of the weight gain induced 
Acta Endocrinol. Suppl . 



de la Torre, R. A. 1974. Mi cro-Hi stol ogi cal Characteristics 
of Three Warm-season Grasses in Relation to Forage 
Quality. Ph.D. Dissertation. University of Florida. 
Gainesville, Florida. 

Dinius, D. A. and B. R. Baumgardt. 1970. Regulation of 

food intake in ruminants. 6. Influence of caloric 
density of pelleted rations. J. Dairy Sci. 53:311. 

Dinius, D. A., J. F. Kavanaugh and B. R. Baumgardt. 1970. 
Regulation of food intake in ruminants. 7. Inter- 
relations between food intake and body temperature. 
J. Dairy Sci. 53:438. 

Dinusson, W. E., F. N. Andrews and W. M. Beeson. 1950. 
The effects of stilbestrol, testosterone, thyroid 
alteration and spaying on the growth and fattening 
of beef heifers. J. Anim. Sci. 9:321. 



147 



Donald, C. M. and W. G. Allden. 1959. The summer nutrition 
of weaner sheep: The deficiencies of the mature her- 
bage of sown pasture as a feed for young sheep. 
Aust. J. Agric. Res. 10:199. 

Donnelly, J. R., J. L. Davidson and M. Freer. 1974. Effect 
of body condition on the intake of food by mature 
sheep. Aust. J. Agr. Res. 25:813. 

Dowden, D. R. and D. R. Jacobson. 1960. Inhibition of 
appetite in dairy cattle by certain intermediary 
metabolites. Nature 188:148. 

Duncan, D. B. 1955. Multiple range and multiple F-tests. 
Biometri cs. 11:1. 

Egan, A. R. 1965. The nutritional status and intake regu- 
lation in sheep. IV. The influence of protein supple- 
ments upon acetate and propionate tolerance of sheep 
fed on low quality chaffed oaten hay. Aust. J. Agr. 
Res. 16:473. 

Egan, A. R. 1966. Nutritional status and intake regula- 
tion in sheep. V. Effects of intraruminal infusions 
of volatile fatty acids upon voluntary intake of 
roughage by sheep. Aust. J. Agr. Res. 17:741. 

Egan, A. R. 1970. Nutritional status and intake regula- 
tion in sheep. VI: Evidence for variation in set- 
ting of a intake regulatory mechanism relating to 
the digesta content of the reticulorumen. Aust. J. 
Agr. Res. 21:735. 

Ellenberger, H. B., J. A. Newlander and C. H. Jones. 1950. 
Composition of the bodies of dairy cattle. Vermont 
Agr. Exp. Sta. Bull. 558. 

Falconer, D. S. 1972. Introduction to Quantitative Genet- 
ics, p. 142-149. The Ronald Press Co., New York. 

Ferguson, K. A. 1956. Efficiency of wool growth. Proc. 
Aust. Soc. Anim. Prod. 1:58. 

Flatt, W. P. and C. E. Coppock. 1963. Fasting metabolism 
of dry, nonpregnant adult dairy cows. J. Dairy Sci. 
46:638 (Abstr.). 

Flemming, D. G. 1969. Humoral and metabolic factors in the 
regulation of food and water intake. Food intake stud- 
ies in parabiotic rats. Ann. N. Y. Acad. Sci. 157:985. 

Foot, J. Z. 1972. A note on the effect of body condition 
on the voluntary intake of dried grass wafers by 
Scottish blackface ewes. Anim. Prod. 14:131. 






148 



Forbes, J. M. 1969. The effect of pregnancy and fatness 
on the volume of rumen contents in the ewe. J. 
Agr. Sci. 72:119. 

Forbes, J. M. 1970. The voTifntary food intake of pregnant 
and lactating ruminants: a review. Brit. Vet. J. 
126:1. 

Fredrickson, D. F. 5 R. I. Levy and R. S. Lees. 1967a. 

Fat transport in lipoproteins - an integrated ap- 
proach to mechanisms and disorders. New England J. 
Med. 276:94. 

Fredrickson, D. F., R. I. Levy and R. S. Lees. 1967b. 

Fat transport in lipoproteins - an integrated ap- 
proach to mechanisms and disorders. New England J. 
Med. 276:215. 

Fredrickson, D. F. , R. I. Levy and R. S. Lees. 1967c. 

Fat transport in lipoproteins - an integrated ap- 
proach to mechanisms and disorders. New England J. 
Med. 276:273. 

Freer, M. and R. C. Campling. 1963. Factors affecting 

the voluntary intake of food by cows. 5. The rela- 
tionship between the voluntary intake of food, the 
amount of digesta in the reti cul o- rumen and the rate 
of disappearance of digesta from the alimentary 
tract with diets of hay, dried grass, or concentra- 
tes. Brit. J. Nutr. 17:79. 

Galleti, F. and A. Klopper. 1964. The effect of progeste- 
rone in the quantity and distribution of body fat 
in the female rat. Acta Endocrinol. 46:379. 



Graham, N. McC. 1964. Maintenance requirements of sheep 
indoors and at pasture. Proc. Aust. Soc. Anim. 
Prod. 5:272. 

Graham, N. McC. 1966. Predicting the maintenance require- 
ments of sheep. Proc. Aust. Soc. Anim. Prod. 6:364, 

Graham, N. McC. 1969. The influence of body weight (fat- 
ness) on the energetic efficiency of adult sheep. 
Aust. J. Agr. Res. 20:375. 

Graham, N. McC. and T. W. Searle. 1972. Balance of energy 
and matter in growing sheep at several ages, body 
weights, and planes of nutrition. Aust. J. Agr. 
Res. 23:97. 



149 



Greaves, M. W.,W. J. McDonald-Gibson and R. G. McDonald- 
Gibson. 1972. The effect of venous occlusion, 
starvation and exercise on prostaglandin activity 
in whole human blood. Life Set. 11:919. 

Greenhalgh, J. F. D. and G. W. Reid. 1973. The effects 
of pelleting various diets on intake and digesti- 
bility in sheep and cattle. Anim. Prod. 16:223. 

Grimes, R. C. 1966. An estimate of the energy required 
for maintenance and live weight gain by young 
grazing sheep. J. Agr. Sci. 66:211. 

Guyton, A. C. 1971. Textbook of Medical Physiology. 
(4th Ed.) p. 915-928. W. B. Saunders Company. 
Philadelphia, Pa. 

,-Hadjipieris, G. and W. Holmes, 1966. Studies on feed in- 
take and feed utilization by sheep. 1. The volun- 
tary feed intake of dry, pregnant and lactating 
ewes. J. Agr. Sci. 66:217. 

Hadjipieris, G. , J. G. W. Jones and W. Holmes. 1965. The 
effect of age and live-weight on the feed intake of 
grazing wether sheep. Anim. Prod. 7:309. 

Hamilton, C. L. and J. R. Brobeck. 1964. Hypothalamic 
hyperphagia in the monkey. J. Comp. Physiol. Psy- 
chol. 57:271. 

Hancock, J. 1952. Grazing behavior of identical twins in 
relation to pasture type, intake and production of 
dairy cattle. In Proc. Intern. Grassld. Conf . , 6th. 
Vol. 2, p. 1399. 

Havel, R. J. 1965. Autonomic nervous system and adipose 
tissue. In: Renold and Cahill (Ed.) Handbook of 
Physiology Section 5: Adipose Tissue. Waverly 
Press, Inc., Baltimore, Maryland. 

Heaney, D. P. 1970. Voluntary intake as a component of 

an index to forage quality. Nat. Conf. Forage Qua!. 
Eval. Util. Proc. (Lincoln, Nebraska), Paper C. 

Hemsley, J. A. and R. J. Moir. 1963. The influence of 

higher volatile fatty acids on the intake of urea sup- 
plemented low-quality cereal hay by sheep. Aust. J. 
Agr. Res. 14:509. 

Hervey, G. R. 1959. The effects of lesions in the hypo- 
thalamus in parabiotic rats. J. Physiol. 145:336. 



' 



150 



Hervey, G. R. 1969. Regulation of energy balance. Nature. 
222:629. 

Hervey, G. R. and E. H. Hervey. 1964. Effects of proges- 
terone on food intake and body composition. J. Endo- 
cri no! . 30 : vi i . 

Hetheri ngton , A. W. and S. W. Ranson. 1940. Hypothalamic 

lesions and adiposity in the rat. Anat. Rec. 78:149. 

Hetherington, A. W. and S. W. Ranson. 1942. The sponta- 
neous activity and food intake of rats with hypotha- 
lamic lesions. Amer. *J . Physiol. 136:609. 

Hill, F. W. and L. M. Dansky. 1954. Studies of the energy 
...■.■retirements of chickens. I. Effect of dietary 
energy level on grov/th and feed consumption. Poul . 
Sci. 33:112. 

Hodgson, J. and J. M . Wilkinson. 1967. The relationship 
between live-weight and herbage intake in grazing 
cattle. Anim. Prod. 9:365. 

Holder, J. M. 1963. Chemostatic regulation of appetite 
in sheep. Nature. 200:1074. 

Holmes, W. , J. G. W. Jones and R. M. Drake-Brockman. 1961. 
The feed intake of grazing cattle. II. The influ- 
ence of size of animal on feed intake. Anim. Prod. 
3:251. 

Houser, R. H. 1970. Physiological Effects of Supplemented 
Nitrogen and Energy in Sheep Fed Low-quality Rough- 
age. Ph.D. Dissertation, University of Florida, 
Gainesville, Florida. 

Huffman, C. F. 1959. Summer feeding of dairy cattle. 
A review. J. Dairy Sci. 42:1495. 

Hungate, R. E. 1966. The Rumen and its Microbes. Academic 
Press. New York. 

Hunter, W. M. and W. M. Regal. 1966. The diurnal pattern 
of plasma growth hormone concentration in children 
and adolescents. J. Endocrinol. 34:147. 

Hutton, J. B., J. W. Hughes, R. P. Newth and K. Watanabe. 
1964. The voluntary intake of the lactating dairy 
cow and its relation to digestion. Proc. New Zea- 
land Soc. Anim. Prod. 24:29. 






151 

Iggo, A. and F. Leek. 1970. Sensory receptors in the rumi- 
nant stomach and their reflex effects. In: A. T. 
Phillipson (Ed.) Physiology of Digestion and Metabo- 
lism in the Ruminant. p. 23. Oriel Press, Limited 
Newcastle upon Tyne, England. ! " 

Ivins, J. D. 1959. The measurement of grassland produc- 
tivity. Proceedings of the University of Nottingham 
Sixth Easter School in Agricultural Science. But- 
terworths Scientific Publications. London. 

Jones, G. M. 1972. Chemical factors and their relation to 
feed intake regulation in ruminants: A review. Can. 
J. Anim. Sci. 52:207. 

Kakolewski, J. W., V. Cox and E. S. Valenstein. 1968. Sex 
differences in body weight change following gonadec- 
tomy of rats. Psychol. Rep. 22:547. 

Karue, C. N., J. L. Evans and A. D. Tillman. 1971. Volun- 
tary dry matter intake and the reference base, W^, 
for growing cattle. J. Dairy Sci. 54:1240. (Abstr.). 

Kay, R. N. B. 1963. Reviews of the progress of dairy 
science. The physiology of the rumen. J. Dairy 
Res. 30:261. 

Kennedy, G. C. 1961. The central nervous regulation of 
calorie balance. Proc. Nutr. Soc. 20:58. 

Kennedy, G. C. and J. Mitra. 1963. Hypothalamic control 

of energy balance and reproduction cycle in the rat. 
J. Physiol. 166:395. 

Kemp, J. D. 1952. Methods of cutting lamb carcasses. 
Proc. Recip. Meat Conf. 5:89. 

Kleiber, M. 1932. Body size and metabolism. Hilgardia 
6:315. 

Kleiber, M. 1961. The Fire of Life - An introduction to 

Animal Energetics. John Wiley and Sons, Inc. New York 

Lampkin, G. H. and J. Quarterman. 1962. Observations on 
the grazing habits of Grade and Zebu cattle. II. 
Their behaviour under favourable conditions in the 
tropics. J. Agr. Sci. 59:119. 

Langlands, J. P. 1968. The feed intake of grazing sheep 
differing in age, breed, previous nutrition and 
live weight. J. Agr. Sci. 71:167. 






152 

Langlands, J. P., J. L. Corbett, I. McDonald and J. D. 

Pullar. 1963a. Estimates of the energy required 
for maintenance by adult sheep. 1. Housed sheep. 
Anim. Prod . 5:1. 

Langlands, J. P., J. L. Corbett, I. McDonald and G. W. 
Reid. 1963b. Estimates of the energy required 
for maintenance of adult sheep. 2 . Grazing sheep. 
Anim. Prod . 5:11. 

Langlands, J. P. and H. A. M. Sutherland. 1968. An 

estimate of the nutrients utilized for pregnancy 
by Merino sheep. Brit. J. Nutr. 22:217. 

Laredo, M. A. and D. J. Minson. 1975. The effect of 

pelleting on the voluntary intake and digestibility 
of leaf and stem fractions of three grasses. Brit. 
J. Nutr. 33:159. 

Larsson, S. 1954. On the hypothalamic organization of food 
intake. Acta Physiol. Scand. 32, Suppl. 115. 

Latham, S. D., W. G. Moody and J. D. Kemp. 1966. Techni- 
ques for estimating lamb carcass composition. J. 
Anim. Sci. 25:492. 

Leek, B. F. 1969. Reti cu 1 o-rumi nal mechanoreceptors in 
sheep. J. Physiol. 202:585. 

Leng, R. A. and D. J. Brett. 1966. Simultaneous measure- 
ments of the rates of production of acetic, propionic 
and butyric acids in the rumen of sheep on different 
diets and the correlation between production rates 
and concentrations of these acids in the rumen. 
Brit. J. Nutr. 20:541. 

Lehninger, A. L. 1970. Biochemistry. p. 417-420. Worth 
Publishers, Inc. New York. 

Lush, J. L. 1956. Animal Breeding Plans. p, 170-179. The 
Iowa State College Press. Ames, Iowa. 

McAtee, J. W. and A. Trenkle. 1971. Effect of feeding, 

fasting and infusion of energy substrates on plasma 
growth hormone levels in cattle. J. Anim. Sci. 33:612. 

MacLusky, D. S. 1955. The quantity of herbage eaten by 

grazing dairy cows. Rep. Brit. Soc. Anim. Prod, p. 45. 

Manns, J. G. and J. M. Boda. 1967. Insulin release by 

acetate, propionate, butyrate, and glucose in lambs 
and adult sheep. Amer. J. Physiol. 212:747. 






153 

Marston, H. R. 1948. Energy transactions in the sheep. 
Aust. J. Sci. Res. Bl:93. 

Martz, F. A.» M. Mishra, J. R. Campbell, L. B. Daniels and 
E. Hilderbrand. 1971. Relation of ambient tempera- 
ture and time postfeeding on ruminal, arterial and 
venous volatile fatty acids, and lactic acid in 
Holstein steers. J. Dairy Sci. 54:520. 

Mather, R. E. 1959. Can dairy cattle be bred for increased 
forage consumption and efficiency of utilization? 
J. Dairy Sci . 42:878. 

Mayer, J. 1955. The physiological basis of obesity and 
leanness. Nutr. Abstr. and Rev. 25:597. 

Mayer, J. 1963. Genetic, traumatic and environmental fac- 
tors in the etiology of obesity. Physiol. Rev. 33: 
472. 

Mayer, J., R. G. French, C. Y. Zighera and R. J. Barnett. 
1955. Hypothalamic obesity in the mouse. Amer. J. 
Physiol. 182:75. 

Miller, W. J., D. M. Blackmon, G. W. Powell, R. P. Gentry 
and J. M. Hiers. 1966. Effects of zinc deficiency 
per se and of dietary zinc level on urinary and endo- 
genous fecal excretion of 6 5z n from a single intra- 
venous dose by ruminants. J. Nutr. 90:335. 

Minson, D. J. 1963. The effect of pelleting and wafering 
on the feeding value of roughage-A review. J. Brit. 
Grass!. Soc. 18:39. 

Minson, D. J. 1971. Influence of lignin and silicon on 
a summative system for assessing the organic matter 
digestibility of Panicum . Aust. J. Agr. Res. 22:589. 

Moir, R. J. 1970. In: A. T. Phillipson (Ed.) Physiology 

of Digestion and Metabolism in the Ruminant. p. 288- 
291. Oriel Press, Newcastle upon Tyne. England. 

Montgomery, M. J. and B. R. Baumgardt. 1965a. Regulation 
of food intake in ruminants. 1. Pelleted rations 
varying in energy concentration. J. Dairy Sci. 48:569 

Montgomery, M. J. and B. R. Baumgardt. 1965a. Regulation 
of food intake in ruminants. 2. Rations varying in 
energy concentration and physical form. J. Dairy Sci. 
48:1623. 






154 



Montgomery, M. J., L. H. Schultz and B. R. Baumgardt. 1963. 
Effect of i ntrarumi nal infusion of volatile fatty 
acids and lactic acid on voluntary hay intake. J. 
Dairy Sci. 46:1380. 

Mowatt, D. N. 1963. Factors Affecting Rumen Capacity and 
the Physical Inhibition of Food Intake. Thesis. 
Cornell University. 

Moore, J. E., E. J. Golding, III, and R. F. Barnes. 1975. 
Assessment of present methods of predicting digesti- 
bility energy values of hays. Prepared for AFGC Re- 
search Committee and Hay Marketing Task Force. April 
1975. 



Moore, 



J. E. and G. 0. Mott. 
of q u a 1 i ty in tropical 
Components of Forages. 
Madison, Wis., Special 



1973. Structural inhibitors 
grasses. In; Anti-Quality 

Crop Sci. Soc. America. 
Publication no. 4, p. 53. 



Moore, 



J. E. and G. 0, 
organic matter 
J . D a i ry Sci. 



Mott. 
from i n 
57:1258 



1974. 
vi tro 



Recovery 
digestion 



of residual 
of forages. 



I e v i 1 1 e , W . E . 
ments of 
33:855. 



1971. Effect of age on the 
lactating Hereford cows. J 



energy 
A n i m . 



requi re- 
Sci . 



N. R. C. 1963. Nutrient Requirement of Domestic Animals, 
No. 4. Pub. 1137. National Academy of Science - 
National Research Council. Washington, D. C. 

N. R. C. 1968. Nutrient Requirements of Domestic Animals, 
No. 5. Nutrient Requirements of Sheep, National 
Academy of Science - National Research Council. 
Washington, D. C. 

O'Brien, C. A., R. E. Bloss and E. F. Nicks. 1968. Effect 
of melengestrol acetate on the growth and reproduc- 
tive physiology of fattening heifers. J. Anim. Sci. 
27:664. 

O'Brien, C. A. and C. F. Miller. 1957. Effect of melen- 
gestrol acetate (MGA) on the reproductive physiology 
and feedlot performance of ewe lambs. J. Anim. Sci. 
26:949. 



Oltjen, R. R., R. E. Davis and R. L. Hiner. 1965. Factors 
affecting performance and carcass characteristics of 
cattle fed al 1 -concentrate rations. J. Anim. Sci. 
24:192. 



155 



Osbourn, D. F., S. B. Cammell , R. A. Terry and G. E. Outen. 
1970. The effect of chemical composition and phy- 
sical characteristics of forages on their voluntary 
intake by sheep. Grassland Res. Inst. Annual Re- 
port, p. 57. 

Owen, J. B., D. A. R. Davies, E. L. Miller and W. J. Ridgman. 
1967. The intensive rearing of lambs. 2. Voluntary 
food intake and performance on diets of varying oat 
husk and beef tallow content. Anim. Prod. 9:509. 

Owen, J. B. and W. J. Ridgman. 1958. Further studies of 

the effect of dietary energy content on the voluntary 
intake of pigs. Anim. Prod. 10:85. 

Preston, R. L. and W. H. Pfander. 1954. Phosphorus meta- 
bolism in lambs fed varying phosphorus intakes. J. 
Nutr. 83:369. 

Pickard, D. W. , H. Swan and G. E. Lamming. 1969. The use of 
ground straw of different particle sizes for cattle 
from twelve days of age. Anim. Prod. 11:543. 

Purser, D. B., T. J. Klopfenstein and J. H. Cline. 1966. 
Dietary and defaunation effects upon plasma amino 
acid concentrations in sheep. J. Nutr. 89:226. 

Purser, D. B. and R. J. Moir. 1966. Rumen volume as a 

factor involved in individual sheep differences. J. 
Anim. Sci . 25:509. 

Quinn, L. R. , G. 0. Mott and W. V. A. Bisschoff. 1958. 

Fertilization of Colonial Guineagrass Pastures and 
Beef Production with Zebu Steers. Bull. 24. IBEC 
Research Institute. 30 Rockefeller Plaza, New York 
20, N. Y. 

Ragsdale, A. C, H. J. Thompson, D. M. Worstell and S. 

Brody. 1950. Environmental physiology with special 
reference to domestic animals. 9. Milk production 
and feed and water consumption responses of Brahman, 
Jersey, and Holstein cows to changes in temperature, 
50° to 105°F and 50° to 8°F. Mo. Agr. Exp. Sta. 
Res. Bull. 460. 

Ragsdale, A. C, H. J. Thompson, D. M. Worstell and S. 

Brody. 1953. Environmental physiology and shelter 
engineering. XXI. The effect of humidity on milk 
production and composition, feed and water consump- 
tion, and body weight in cattle. Mo. Agr. Exp. Sta. 
Res. Bull. 521. 



156 



Radloff, H. D., L. H. Schultz and W. G. Hoekstra. 1966. 
Relationship of plasma free fatty acids to other 
blood components in ruminants under various physio- 
logical conditions. J. Dairy Sci. 49:179. 

Rimm, A. A., R. E. Mather and J. W. Bartlett. 1957. 

Relationship of roughage consumption to body size 
and its repeatability in dairy heifers. American 
Society of Animal Production. Annual Meeting. Novem- 
ber 30, Chicago, Illinois. 



Ritzman, E. G. and F. G. Benedict. 1938. 
Physiology of the AduU Ruminant. 
Washington Pub. 494. 



Nutri ti onal 
Carnegie Inst 



Ritzman, E. G. and N. F. Colovos. 1943. Physiological 

requirements and utilization of protein and energy 
by growing dairy cattle. N. H. Agri. Exp. Sta. 
Tech. Bull. 80. 

Rook, J. A. F., C. C. Balch and R. C. Campling. 1960. The 
effects of intraruminal infusions of acetic, propionic 
and butyric acid on nitrogen retention in the growing 
heifer. Proc. Nutr. Soc. 19:i. 

Rubner, M. 1883. Uber den Einfluss der Korpergrosse auf 
Stoffund Kraftwechsel . Z. f. Biol. 19:535. 

Seoane, J. R. 1971. Studies on Feed Intake Regulation in 
Sheep Using a Cross-circulation Technique. Ph.D. 
dissertation. Cornell University, Ithaca, N. Y. 

Seoane, J. R. and C. A. Baile. 1973. Ionic changes in 

cerebrospinal fluid and feeding, drinking and temper- 
ature of sheep. Physiol. Behav. 10:915. 

Seoane, J. R. , C. A. Baile and H. F. Martin. 1972a. Humoral 
factors modifying feeding behavior of sheep. Physiol. 
Behav. 8:993. 

Seoane, J. R. , C. L. McLaughlin and C. A. Baile. 1975. 

Feeding following i ntrahypothal ami c injections of 

calcium and magnesium ions in sheep. J. Dairy Sci. 
58:349. 



Seoane, J. R. and R. G. Warner. 1971. A technique for 
cross-circulating blood of anesthetized sheep. J 
Anim. Sci. 32:1174. 



157 



Seoane, J. R. , R. G. Warner and N. A. Seoane. 1972b. 

Heparin- induced li polys is and feeding behavior in 
sheep. Physiol. Behav. 9:419. 

Service, J., A. J. Barr and J. H. Goodnight. 1972. SAS-A 
User's Guide to the Statistical Analysis Systems. 
North Carolina State University, Raleigh, N. C. 

Simkins, K. !_., J. W. Suttie and B. R. Baumgardt. 1965. 

Regulation of food intake in ruminants. 4. Effect 
of acetate, propionate, butyrate and glucose on 
voluntary intake in dairy cows. J. Dairy Sci . 48: 
1635. 

Snedecor, G. W. and G. W. Cochran. 1967. Statistical 
Methods (6th Ed.). Iowa State University Press. 
Ames. Iowa. 

Steinbaum, E. A. and N. E. Miller. 1965. Obesity from 

eating elicited by daily stimulation of hypothalamus. 
Amer. J. Physiol. 208:1. 

Swiger, L. A. W. R. Harvey, D. 0. Everson and K. E. Gregory. 
1964. The variance of intraclass correlation involv- 
ing groups with one observation. Biometrics 20:818. 

Tarttelin, M. F. and F. R. Bell. 1968. The effects of 

hypothalamic lesions on food and water intake in 

sheep. Third Inter. Conf. in the Regulation of 
Food and Water Intake, Haverford College. 

Tayler, J. C. 1959. A relationship between weight of in- 
ternal fat, 'fill', and the herbage intake of grazing 
cattle. Nature. 184:2021. 

Taylor, St. C. S. and G. B. Young. 1968. Equilibrium weight 
in relation to food intake and genotype in twin 
cattle. Anim. Prod. 10:393. 

7-iitelbaum, P. and A. N. Epstein. 1962. The lateral hypo- 
thalamic syndrome: Recovery of feeding and drinking 
after lateral hypothalamic lesions. Psychol. Rev. 
69:74. 

Telle, P. P., R. L. Preston, L. 0. Kintner and W. H. Pfander . 
1964. Definition of the ovine potassium requirement. 
J. Anim. Sci. 23:59. 

Terry, R. A., S. B. Cammell and D. F. Osbourn. 1972. Fac- 
tors influencing the digestion of sugars, starches 
and the cell wall constituents in feeds. Grassland 
Res. Inst. Annual Report. p. 88. 






158 



Theurer, B., W. Woods and G. E. Poley. 1966. Comparison 
of porta] jugular blood plasma amino acids in lambs 
at various intervals postprandial. J. Anim. Sci. 
25:180. 

Thonney, M. L. R. W. Touchberry, R. D. Goodrich and J. C. 
Meiske. 1 974 . Reevaluation of metabolic body 
weight (W»75). j. Anim. Sci. 39:1002. (Abstr.). 

Thye, F. W. , R. G. Warner and P. D. Miller. 1969. Rela- 
tionship of various blood metabolites to voluntary 
feed intake in lactating ewes. J. Dairy Sci 52- 
908. (Abstr.). 

Thye, F. W., R. G. Warner and P. D. Miller. 1970. Rela- 
tionship of various blood metabolites to voluntary 
feed intake in lactating ewes. J. Nutr. 100:565. 

Tilley, J. M, A. and R. A. Terry. 1963. A two stage 

technique for i_n vitro digestion of forage crops 
J. Brit. Grassl. Soc. 18:104. 

Trenkle, A. 1970. Effects of short-chain fatty acids, 

feeding, fasting and type of diet on plasma insulin 
levels in sheep. J. Nutr. 100:1323. 

Trenkle, A. and K. V. Kuhlemeier. 1966. Relationship of 
rumen volatile acids, blood glucose and plasma non- 
esterified fatty acids in sheep. J. Anim. Sci. 25: 

Troelsen, J. E. and J. M. Bell. 1963. A comparison of 
nutritional effects in swine and mice. Responses 
in feed intake, feed efficiency and carcass charac- 
teristics to similar diets. Can. J. Anim Sci 43- 
294. 

Troelsen, J. E. and J. B. Campbell. 1968. Voluntary con- 
sumption of forage by sheep and its relation to the 
size and shape of particles in the digestive tract 
Anim. Prod. 10:289. 

Tulloh, N. M. 1966. Physical studies of the alimentary 
tract of grazing cattle. IV. Dimensions of the 
tract in lactating and non- 1 actati na cows. New 
Zealand J . Agr. Res, 9:999. 

Turner, H. N. and S. Y. Young. 1969. Quantitative Genetics 
in Sheep Breeding. p. 77-93. Cornell University 
Press. Ithaca, New York. 






159 

Ulyatt, M. J. 1964. Studies of some factors influencing 
food intake in sheep. New Zealand Soc. Anim. Prod. 
24:43. 

Ulyatt, M. J. 1965. The effects of intraruminal infusions 
of volatile fatty acids on food intake of sheep. 
New Zealand J. Agric. Res. 8:397. 

Ulyatt, M. J., K. L. Blaxter and I. McDonald. 1967. The 
relations between the apparent digestibility of 
roughages in the rumen and lower gut of sheep, the 
volume of fluid in the rumen and voluntary feed in- 
take. Anim. Prod. 9:463. 

Underwood, E. J. 1962. Trace Elements in Human and Animal 
Nutrition. Academic Press, New York. 

Van Itallic, T. B. and S. A. Hashim. 1960. Biochemical 
concomitants of hunger and satiety in man. Amer. 
J. Clin. Nutr. 8:587. 

Van Soest, P. J. 1965. Symposium on factors influencing 

the voluntary intake of herbage by ruminants: Volun- 
tary intake in relation to chemical composition and 
digestibility. J. Anim. Sci. 24:834. 

Van Soest, P. J. 1967. Development of a comprehensive 

system of feed analysis and its application to for- 
ages. J. Anim. Sci. 26:119. 

Van Soest, P. J. 1968. Structural and chemical charac- 
teristics which limit the nutritive value of forages, 
p. 63-76. In: C. M. Harrison (Ed.) Forage Economics- 
Quality. Spec. Publ. 13. Amer. Soc. of Agron., 
Madison, Wis. 

Van Soest, P. J. 1969. Newer knowledge of the composition 
and methods of analysis of feeding stuffs. In: I. 
D. Cuthbertson (Ed.) Nutrition of Animals of Agricul- 
tural Importance. Part I. Pergamon Press Ltd. London. 

Van Soest, P. J. and R. H. Wine. 1967. Use of detergents 

in the analysis of fibrous feeds. IV. Determination 
of plant cell-wall constituents. J. A. 0. A. C. 50:50. 

Velasquez, J. A. 1974. Prediction of In Vivo Digestibility 
in Warm Season Grasses by Summative Equations and In 
Vitro Digestions. M.S. Thesis. University of Florida. 

Ventura, M., J. E. Moore, 0. C. Ruelke and D. E. Franke. 

1975. Effect of maturity and protein supplementation 
on voluntary intake and nutrient digestibility of 
Pangola digitgrass hays. J. Anim. Sci. 40:769. 



160 



Wade, G. N. and I. Zucker. 1970. Development of hormonal 
control over food intake and body weight in female 
rats. J. Comp. Physiol. Psychol. 70:213. 

Walker, D. W. and N. R. Remley. 1970. The relationship 

among percentage body weight loss, circulating free 
fatty acids and consummatory behavior in rats. 
Physiol. Behav. 5:301. 

Welch, J. G. 1967. Appetite control in sheep by indiges- 
tible fibers. J. Anim. Sci. 26:849. 

Weston, R. H. 1966. Factors limiting the intake of feed 
by sheep. I. The significance of pal atabi 1 i ty , the 
capacity of the alimentary tract to handle digesta, 
and the supply of glucogenic substrate. Aust. J. 
Agr. Res. 17:939. 

Weston, R. H. 1967. Factors limiting the intake of feed 
by sheep. II. Studies with wheaten hay. Aust. J. 
Agri. Res. 18:983. 

Weston, R. H. 1968. Factors limiting the intake of feed 
by sheep. I'll. The mean retention time of feed 
particles in sections of the alimentary tract. 
Aust. J. Agri. Res. 19:261. 

Weston, R. H. and J. P. Hogan. 1973. Nutrition of herbage 
fed ruminants. In: Alexander and Williams (Ed.) 
The Pastoral Industries of Australia. Sydney Univer- 
sity Press. Sydney. 

Winegrad, A. I. 1962. Endocrine effects on adipose tissue 
metabolism. Vit. and Horm. 20:141. 

Woods, W. and R. W. Rhodes. 1962. Effect of varying 

roughage to concentrate rations on the utilisation 
by lambs of rations differing in physical form. 
J. Anim. Sci. 21:479. 

Worstell, D. M. and S. Brody. 1953. Environmental physi- 
ology and shelter engineering. XX. Comparative 
physiological reactions of European and Indian 
cattle to changing temperature. Mo. Agr. Exp. Sta. 
Res. Bull. 515. 






BIOGRAPHICAL SKETCH 

Fausto A. Capote was born on August 11, 1938, at 
Cienfuegos, Cuba. In 1957, upon receiving the degree of 
Bachiller en Ciencias from Colegio Maristas, he entered the 
University of Florida, and was granted the degree of Bachelor 
of Science in Agriculture in December, 1962. He enrolled in 
the Graduate School of the University of Florida and gradu- 
ated with the degree of Master of Science in Agriculture in 
April, 1964. 

In November, 1964 he joined the staff of the Escuela 
Agricola Panamericana at Zamorano, Honduras, to teach several 
courses in Animal Science. Since January 1967, he has been 
in charge of the teaching and research programs in animal 
nutrition at the Facultad de Ciencias Veterinarias of the 
Universidad del Zulia, Maracaibo, Venezuela. 

In September 1972, he was awarded a fellowship by the 
Universidad del Zulia to continue graduate work. At present 
he is a candidate for the degree of Doctor of Philosophy in 
the Department of Animal Science, University of Florida. 

Fausto A. Capote is married to the former Amelita 
Morales Salazar, and is the father of two children, Maria 
Isabel and Fausto III. 

The author is a member of Gamma Sigma Delta Honor 
Society. 

161 






I have read this study and that 



i n my 



I certify that 
opinion it conforms to acceptable standards of scholarly* 7 
presentation and is fully adequate, in scope and quality 
as a dissertation for the degree of Doctor of Philosophy 




rlryu- 



John E. Moore, Chairman 
Jrofessor of Animal Science 



} certify that I have read this study and that in my 
opinion. it conforms to acceptable standards of scholarly 
presentation and is fully adequate, in scope and quality, 
as a dissertation for the degree of Doctor of Philosophy 




*&**t-JLK^ 




^222^k^^h 



Clarence B. AmmermaTT 
Professor of Animal Science 



I certify 
opinion 
pre 
as 



that I have read this study and that 



i n my 



imon it conforms to acceptable standards of scholarly 

ssentation and is fully adequate, in scope and quality 

a dissertation for the degree of Doctor of Philosophy 






ft. A 



yc 



Lee McDowell 
Assistant Professor of 
Animal Science 



I certify 
opinion 
prese 
as a d 



that I have read this study and that 



i n my 



on it conforms to acceptable standards of scholarly 
ntation and is fully adequate, in scope and quality, 
dissertation for the degree of Doctor of Philosophy 




Jt UU 



d 



c_ 



Gerald 0. Mott 
Professor of Agronomy 



I certify that I have read this study and that in my 
opinion it conforms to acceptable standards of scholarly 
presentation and is fully adequate, in scope and quality, 
as a dissertation for the degree of Doctor of Philosophy. 

UboiCk* X LOjl£Lc. c f*. 

Charles J. Wilcox ' 

Professor of Dairy Science 

This dissertation was submitted to the Graduate Faculty 
of the College of Agriculture and to the Graduate Council, 
and was accepted as partial fulfillment of the requirements" 
for the degree of Doctor of Philosophy. 

December, 1975 

pean/, College of agriculture 
Dean, Graduate School .